I got The Noble Wild a month or two ago, and am preparing to run a campaign using it. My group uses Pathfinder rather than 3.5, though, so I was preparing to update everything to PF1 when I came across Skirmisher Game Development's Pathfinder version of the same book. Well...I say "preparing," but I'd actually written up 90% of an overhauled base class, the Greater Familiar.

Even if I don't end up using this homebrew, I want to get something out of it. So I'd like your opinions on how well I did, regarding:
1. How interesting you think the class would be to play.
2. How balanced it is as a (support) character in its own right.
3. How balanced it is as a companion (ie cohort) to another player character.
It was tricky figuring out whether this was balanced. On one hand, it's clearly less powerful than a typical spellcaster; on the other hand, A. that's not necessarily an ideal balance point and B. by design it's empowering a group of characters including some of the most easily abused classes in the game. Also, I don't have a lot of experience with homebrew classes.

Spoiler: Discussion of the original class and my goals in the new design

The Greater Familiar is a neat idea—it's a class for animals (or sometimes humanoids) who want to make better familiars. (This isn't odd, considering that the entire book is for animal player characters.) The execution is...lacking. You get the abilities a familiar would normally get from its master at about the same level as they would normally be granted (sometimes a level later), which feels incredibly redundant. You can counter spells, but only a few times per day—a 1st-level familiar can counter two cantrips per day, which almost feels more insulting than not being able to counter at all. All other spell levels can be countered a level later than wizards can cast them, your maximum counterspells/day are scarcer than any primary caster's spells per day (including a cleric without domain spells), and you still need to make a Spellcraft check to identify the spell (though obviously you don't need to have the spell known/prepared, so it's not a total wash). You also get three metamagic feats that you can apply specifically to your master's spells (no details on how this works—including big things like "does it raise the spell level"—are provided), the ability to scry on your master two levels after you let your master scry on you, and a little note which forbids you from ever casting spells (because what kind of magical servant can use magic?)
TL;DR: You can counter a few meaningful spells per day (and eventually a bunch of outmoded ones) and give your master a couple of metamagic feats. And eventually, you can scry on your master. Other than that, you're a normal familiar.

I wanted to keep the feeling of a caster support character, and the counterspell focus was neat so I'd keep that, but I wanted to give the familiar more things to do when there weren't spells to counter. The people at Skirmisher evidently didn't feel the same; they added two high-level abilities (teleporting to the master and restoring cast spells), made bonus feats more flexible and (slightly) more numerous, and shuffled around a few abilities (mostly delaying when they're acquired). Oh, and greater familiars don't have dedicated slots for countering cantrips...not that they have any more slots for countering other spells, mind.

Another thing I wanted to do that I can absolutely understand Skirmisher not wanting to touch is opening the door to a more...sinister master/familiar relationship. Ones where the master and familiar are in conflict, or where the familiar is dominant over the relationship. This was partly inspired by the quasi-Faustian nature of witch familiars in Pathfinder, partly by a couple of abilities in the original greater familiar class that the familiar could explicitly deny to its master, and partly by Wildbow's Pact and Pale, where making too powerful a being into your familiar has some serious negative consequences.

Spoiler: General Information

Many spellcasters bond with an animal, granting it a measure of intelligence and magical power. These animals, known as “familiars,” are as iconic as a wizard’s spellbook or staff. But while books and staves are almost never independently imbued with magic, animals frequently are.
Some are simply born with it; others stumble onto sources of natural magic or artificial contamination; still others are familiars who lost their masters but retain some of the power they were granted. Out of these magical animals, most live largely normal lives, a bit tougher and smarter than most animals. However, some seek out partners who can use and enhance their innate magical abilities. These make more powerful, though more willful, familiars than ordinary animals, and are hence called “greater familiars”.
Note: For clarity, the familiar is referred to as “it,” and the master as “they”.

Alignment: Any. A greater familiar bonding with a master more than one step away from them (on either alignment axis) is likely to cause discord between the two.
Hit die: d8
Class Skills
The greater familiar’s class skills are are Escape Artist (Dex), Fly (Dex), Knowledge (all) (Int), Profession (Wis), Spellcraft (Int), and Tumble (Dex).
Skill ranks per level: 2 + Int modifier

Spoiler: Class Table

I didn't really want to transcribe a 20-level class table into BBCode for a class I realized I didn't need after all, so I just screenshotted it. My apologies for the inconvenience and how badly I centered the screenshot over the image.

Spoiler: Ability Descriptions

Arcane Bond (Ex or Sp): At 1st level, greater familiars form a powerful bond with an arcane spellcaster. If the familiar is a player character, this spellcaster must be another player character, a cohort, or another NPC previously tied to the party. This spellcaster is herein referred to as the familiar’s master; however, the familiar does not need to serve the master. The two may be equals, particularly if both are player characters; if the familiar’s level is higher than the master’s (for instance, if the master is the familiar’s cohort), the “master” may be subservient to its familiar.
The master does not necessarily need to be capable of obtaining an ordinary familiar (e.g. through a wizard’s Arcane Bond feature); however, if they have another familiar, it must be dismissed before the greater familiar can forge a new bond. Bonding to a master requires a specialized ritual costing 200 gp per level of the wizard or greater familiar, whichever is higher. (This is the same ritual as a wizard or other spellcaster uses to bind a familiar; a separate ritual to bind the master to their familiar is not required.)
If the master could normally obtain a familiar, the greater familiar gains all the benefits that familiar would normally receive except for an altered Intelligence score and the statistics noted under Familiar Basics. Some of a familiar’s class abilities will function differently if their master provides a certain benefit; these are specifically noted in the ability description. For the purpose of this class, all abilities which a familiar would gain from its master’s class levels qualify as benefits, even if they exclusively affect the master.
A greater familiar generally cannot have a familiar archetype applied. (If I was going to continue rewriting this class, I might turn some into class archetypes, make rules for applying certain familiar archetypes to greater familiars, or both.)
A greater familiar occasionally obtains a familiar (e.g. through multiclassing or the Familiar Bond feat), but this is rare. In such situations, there is effectively no bond between the familiar’s master and its familiar; they do not share an empathetic link, cannot share spells, etc. It is theoretically possible for a greater familiar to have another greater familiar as its familiar, but no examples of such are known.

Counterspells (Sp): While a greater familiar generally lacks the ability to cast spells independently of its master, it can use its innate magic to disrupt other spells. This functions as the counterspell function of dispel magic, except as noted.
As with normal counterspelling, the familiar must ready an action to counter an enemy spell. It may still move at its normal speed, since ready is a standard action. If that enemy casts a spell, the familiar may immediately attempt to counter it. Its effective caster level for the dispel check is equal to either its Greater Familiar level plus its highest arcane caster level (if applicable), or the caster level of its master (if higher).
A greater familiar can only counter a limited number of spells per day, as indicated in the table (under Counterspells Per Day). Each counterspell use has a maximum useful level; a counterspell use can counter a spell lower than its level, but not greater. The familiar automatically knows the spell level of any spell it attempts to counter, and does not expend a counterspell use if the spell is too powerful for it to counter. The familiar gains bonus counterspells per day for high ability scores as a spellcaster gains bonus spells, using whichever ability score its master uses for that purpose. (For instance, a wizard’s greater familiar would gain extra counterspells for a high Intelligence.)
If the familiar and its master come into conflict, the familiar can counter its master’s spells more easily than most. It cannot use its master’s caster level on the dispel check, but adds five to its effective caster level. In addition, it may expend a counterspell one level lower than the spell.

Empathic Link (Su): The familiar has an empathic link with its master to a 1 mile distance. The familiar can communicate empathically with the master, but cannot see through its eyes. Because of the link’s limited nature, only general emotions can be shared. The familiar has the same connection to an item or place that its master does.

Evasion (Ex): When subjected to an attack that normally allows a Reflex saving throw for half damage, a familiar takes no damage if it makes a successful saving throw.

Gift of Understanding (Su): As long as a greater familiar has a bonded master, it can perceive magic from their realm even if it is from the other realm. You gain the Gift of Understanding feat as a bonus feat, even if you do not meet its prerequisites. This feat goes away if you lose or leave your master.
If the Magical Transparency rules on page 119 of The Noble Wild are not in play, or if both master and familiar are from the same realm (ie, both animals or both humanoids), this ability has no effect.

Natural Armor Adjustment: A familiar’s hide is tougher than that of an ordinary animal of its kind. Its natural armor increases by the amount shown on the table. This does not stack with the similar adjustment provided by the master’s Natural Armor Adjustment benefit. If the bonus provided by the greater familiar’s class levels and the master’s arcane bond are equal, the familiar gains an additional +1 bonus to natural armor; otherwise, it simply uses the higher value.

Alertness (Ex): Starting at 2nd level, a greater familiar gains the Alertness feat within arm’s reach of its master. If the master would grant the Alertness benefit, as long as familiar and master are within arm’s reach, the familiar may use the master’s Perception or Sense Motive modifier if it is higher, and vise versa.

Master Benefits (Su): Just as the master takes on aspects of their familiar, the familiar takes on aspects of their master. At 2nd level, a greater familiar who is currently bonded to a master gains a benefit depending on the master’s race.
Drow Familiar gains a +3 bonus to Perception checks underground
Dwarf Familiar gains a +2 bonus on saving throws against magical effects
Elf Familiar gains a +3 bonus to Perception checks outdoors
Giant Familiar gains +3 hit points
Gnome Familiar can cast ghost sound and prestidigitation at will
Goblin Familiar gains a +3 bonus to Stealth checks
Grippli Familiar gains +3 hit points
Halfling Familiar gains a +3 bonus to Acrobatics checks
Human Familiar gains a +3 bonus to Diplomacy checks
Kobold Familiar gains a +2 bonus to Craft (Trapmaking) checks and may attempt to craft traps without needing appropriate tools or appendages
Lizardfolk Familiar gains a +3 bonus to Climb checks
Merfolk Familiar gains a +3 bonus to Swim checks
Noble animal As the familiar benefit for an equivalent animal (e.g. +2 to Reflex saves for a noble weasel).
Orc Familiar gains a +3 bonus to Intimidate checks
Planetouched (any) Familiar gains a +3 bonus to Knowledge (the planes) checks
Tengu Familiar gains a +3 bonus to Appraise checks
Masters with ancestry from multiple races may grant a master benefit from any of those races; for instance, a half-elf master could grant a bonus to Perception checks or Diplomacy checks. If the master is of a race not listed above, the DM should check the list of familiar benefits on page 69 of The Noble Wild or select an appropriate bonus of comparable value.

Share Spells (Su): Starting at 2nd level, a greater familiar’s master may cast a spell with a target of “You” on his familiar (as a touch spell) instead of on themself. They may cast spells on the familiar even if the spell does not normally affect creatures of the familiar’s type. If the familiar can cast spells, they can likewise share spells with their master.
If the master would grant the Share Spells benefit, either master or familiar may cast a spell with a target of “You” on both master and familiar, as long as both remain in contact for the spell’s entire duration. If they separate while the spell is still active, only the original caster of the spell remains affected.

Deliver Touch Spells (Su): If a greater familiar is 3rd level or higher, it can deliver its master’s touch spells for them. If the master and the familiar are in contact at the time the master casts a touch spell, they can designate the familiar as the “toucher.” It can then deliver the touch spell just as the master would. As usual, if the master casts another spell before the touch is delivered, the touch spell dissipates.
If the master would grant the Deliver Touch Spells benefit, the master and familiar do not need to be in contact when the spell is cast. In this case, they must have line of effect to one another when the spell is cast.

Spellcasting: A greater familiar’s innate magical capabilities allow them to mimic it’s master’s spellcasting. It can cast any arcane spell its master knows or has prepared. For all relevant purposes (such as metamagic use), these spells count as spontaneously cast. If non-humanoid, the familiar can provide any verbal and somatic components required by performing motions and vocalizations appropriate to its kind; it requires direct access to material components and foci. (Large familiars may have their own material component pouches, but most will need access to their master’s.)
While the familiar can use its master’s spells, it does not expend their spell slots or spells prepared. Instead, it must expend a use of counterspell one level higher than the spell’s level. (For instance, casting magic missile would require expending a second-level counterspell use.) It is still treated as a spell of its original level, ie the level which its master casts the spell at.
Moreover, the familiar uses its own caster level (equal to its Greater Familiar level plus its highest arcane caster level, if any) rather than its master’s. Saving throw DCs and the like are based off of the familiar’s ability score; its casting attribute is the same as its master’s (i.e. Intelligence for a wizard’s familiar). The familiar may choose to treat itself as a creature of its caster’s type for the purpose of spells with a target of “You” (e.g. alter self).
As a familiar can counter its master’s spells, so can a master easily counter its familiar’s spells. This functions as the counterspell function of dispel magic, and requires expending a spell slot or prepared spell with a level one less than the countered spell’s effective spell level.
This spellcasting ability can be used to qualify for feats, prestige classes, and so on. If a prestige class increases spells per day by “+1 level of existing class,” the greater familiar may instead increase their counterspells per day as if it had also gained a level of greater familiar. It does not, however, gain other benefits a character of that class would have gained, except for additional counterspells per day and a higher caster level for counterspells and spellcasting.

Speak With Master (Ex): If the familiar is 5th level or higher, it and its master can communicate verbally as if they were using a common language. Other creatures do not understand the communication without magical help.
If the master would grant the Speak With Master benefit, they can also communicate telepathically while within one mile of each other. (This only allows them to communicate; neither can use the other’s senses.)

Speak With Animals (Ex): A non-noble greater familiar of at least 6th level can communicate with animals of approximately the same kind as itself. If its master would grant the Speak With Animals benefit, the familiar may instead communicate with all animals.
However, a greater familiar will generally be a noble animal, innately capable of speaking with other animals of its kind, and often animals of other kinds. Noble animals instead gain the ability to communicate with all animals, whether or not they share a language. If its master would grant the Speak With Animals benefit, the familiar may also communicate with vermin.
In all cases, such communication is limited by the Intelligence of the conversing creatures. Greater familiars are generally more adept at communicating with wild creatures than their artificially-uplifted counterparts, but a cat is still a cat.

Master Metamagic (Su): At 7th level, it gains any metamagic feat as a bonus feat. (It must still meet any prerequisites for that feat, if applicable.) Of course, the greater familiar can apply metamagic feats to spells it casts, but it can also alter its master’s magic.
A greater familiar may choose to retract this benefit from its master. If the master casts spells spontaneously, they can no longer use those feats. If the master prepares spells, any metamagic spells prepared with the familiar’s aid cannot be cast without the familiar’s agreement.
A greater familiar gains further bonus metamagic feats at 13th and 19th level.

Improved Evasion (Ex): When subjected to an attack that normally allows a Reflex saving throw for half damage, a greater familiar of at least 8th level takes half damage even if the saving throw fails (in addition to taking no damage on a successful save). If its master would grant the Improved Evasion benefit, the familiar gains Lightning Reflexes as a bonus feat.

Spell Echo (Sp): Many spells can be shrugged off by a potent opponent. A greater familiar can force such an opponent to resist the spell again.
This ability may only be used if a target of a spell its master cast in the last round was completely unaffected by it, whether due to a successful saving throw, spell resistance, or some other ability. As a full-round action, the familiar may cause that spell to affect the target again. The target may attempt another saving throw (if applicable), and abilities like spell resistance still apply.
This ability may only be used on spells which directly affect the target; for instance, it does not apply to a creature which is missed by a summoned creature or animated object, nor one which secures itself in a reverse gravity field. It also does not apply if the target was only partially affected by a spell due to a successful saving throw; for instance, while it could be used on someone who passed baleful polymorph’s Fortitude save (and was not transformed into an animal), it could not be used on someone who only passed the Will save (and was). If the spell would normally deal half damage on a successful save, but dealt no damage due to the target possessing evasion or a similar ability, Spell Echo cannot be used on that target.

Spell Resistance (Su): Starting at 11th level, a familiar gains spell resistance equal to its class level +5 (or its master’s caster level +5, if higher). If the master would grant the Spell Resistance benefit, the master also gains spell resistance.

Scry On Master (Sp): Starting at 15th level, a greater familiar may scry on its master (as if casting the scrying spell) once per day.
I did not decide on abilities for 17th or 20th level. The Teleport To Master and Arcane Recharge abilities which Skirmisher Publishing added could work, though?

Spoiler: Favored Class Bonuses

For those who don't know, favored classes work differently in Pathfinder than they did in 3.5. Everyone gets to choose a favored class; each time they take a level in that class, they get +1 hit point, +1 skill point, or a special bonus that varies by class and race. The following are the unique favored class bonuses for greater familiars.

Bat: When you or your master cast a spell from the illusion (shadow) subschool or with the darkness descriptor, add +½ to the caster level.
Cat: When casting illusion spells, add 1 to the caster level, but only for determining the duration.
Hawk: When casting divination spells, add ½ to the caster level.
Lizard: Add 1 to your effective caster level for the purpose of counterspelling.
Monkey: Your master gains one skill point. These skill points are lost if the bond between you and your master is broken. If you later gain a new master, you may grant them these skill points.
Owl: Choose one spell on your master’s spell list which is at least one level below the highest-level spell they can cast. They learn that spell (if a spontaneous spellcaster) or add it to their spellbook for free (if not). The ability to cast these spells is lost if the bond between you and your master is broken. If you later gain a new master, you may select new spells for them to learn.
Rat: When your master shares a spell with you, add ½ to the caster level. If the spell affects the master as well, only increase the caster level for its effects on you.
Raven: Learn 1/5 of a spell. Treat it as a spell learned through the Familiar Spellcasting feat, including restrictions on which spells may be learned.
Snake: When using a natural attack to deliver a touch spell, add +½ to your attack roll.
Toad: Your master gains one hit point. These hit points are lost if the bond between you and your master is broken. If you later gain a new master, you may grant them these hit points.
Weasel: When using a natural attack to deliver a touch spell, add +1 to your damage roll. (This is applied to the damage you deal, not to the spell’s damage.)

Spoiler: New feat: Familiar Spellcasting

The energy imbued in a familiar is usually formless, almost impossible to shape into spells without aid. However, some learn to cast spells of their own, drawing on their master's experience by bond and observation alike.
Prerequisites: Greater Familiar, able to counter 3rd-level spells
Benefits: You learn one spell at least two levels below the highest-level spell you can counter. (For instance, a 9th-level greater familiar can counter 4th-level spells and could select a spell of 1st or 2nd level.) This spell must be on the spell list of an arcane spellcasting class your master has at least one level in. For all relevant purposes, including spell level, it counts as an arcane spell cast by a member of that class.
You may cast this spell by expending a counterspell use one level higher than the spell, as normal. If you would ordinarily be able to cast the spell through your Greater Familiar spellcasting ability (ie, if your master knows or prepared the spell), you may instead expend a counterspell use of the spell’s level; this does not affect the effective spell level.
Just as a familiar can gain spellcasting abilities from its master, so can a master gain spells from their familiar. A master who prepares spells may prepare any spell their familiar knows through this feat; one who casts spontaneously may treat any spell their familiar knows through this feat as though they knew it. They must already be able to prepare or cast spells of the appropriate level.
You retain knowledge of these spells even if you lose your master. You can continue to cast them as normal. If you later gain another master, they may cast spells you know, whether or not they are on their spell lest.
Special: This spell may be taken more than once. Each time, you select a new spell to learn.