I'm thinking of DMing a campaign on my forums with a world I've been dreaming up, and have been doing some class tinkering to try and balance it. I haven't got into the real crunch (no statting the changes out) yet (still planning them), but here's the deal:

The world is blessed with ambient energy, magic some call it. Periodically, it is bombarded with bizarre, meteorlike objects. There are two varieties of these, Seeds of Life, and Seeds of Void. When Seeds of Life hit, they deposit varieties of objects and such. Sometimes as mundane as good planting soil, other times they deposit blessing, such as new species of live stock and crops, magical items, or even the beginning population of new races, fully formed and matured with no memory of their pasts. When a Seed of Void strikes, it instantly disintegrates everything within a certain radius, leaving only the Seed nestled in the crater. These seeds are supposedly sent by respectively the Lord of All, a creator deity, and the Lord of Nil, a destroyer deity.

The planet is warmest (virtually unlivable) toward the North Pole, and frigid cold at the south, with the most balanced temperatures occuring at the Equator. This is due to two beasts, Ignis of Flame, and Inej of Ice, making their homes at the respective poles. Their power ebs and flows with the number of followers that either one has, leading to changing climates world over.

Religions exist, but have no allignment restrictions. An evil being may desire the power of the Lord of All to structure and organize the world, while a good character may find inspiration in the Lord of Nil's ability to purify and purge the world of corruption.

Magic as a whole is generally not studied, thus no Wizard class. People recognize the phenomena around them, and know well of it, but usually do not attempt to learn to harness it for their own gain.

So, with my setting presented, my changes to the classes:
All class skills will be revised. I'm thinking of making some basic skills Class skills for anybody (Spot, Listen).

Druid: Warriors that can warp the ambient energy of the world around them to transform themselves and strengthen others. They have a great respect for nature, though much of that is tied to fearing accidentally injuring their colleagues.
Changes: Probably one of my more extreme. Instead of spells, they'll pick and choose new animal forms based on level that they can turn into. I'll probably be significantly powering up that ability, though taking away a few of their other ones (namely most of their spellcasting, and downsizing their animal companion to be even with Rangers). I think I'll remove most of the summoning, and replace it with healing instead. I want to have a class that's more paladin in capability. Healing and melee, neither one AS good as a cleric or fighter, but with versatility instead.

Sorceror: People, who, from birth, have been gifted with a natural control over the energy surrounding them. They cast by a variety of gestures and actions that instinctively lead to spells.
Changes: No Familiar. Doesn't need spell components. When they level up, they instantly know spells to their maximum ammount of spells known, which are tied to physical gestures. Players may request spells, and the gestures tied to them, of the DM, but where they are not chosen, the DM fills in the choices for them. (And the DM gets the final say. If a DM were a jerk, this could be ugly, but this is moreso a safety check to prevent any borken material)

Cleric: People who specialize in channeling the divine energy present in their holy symbol. Their holy symbols are made of either the respective seed, or an actual piece of horn/hoof or shell from Ignis or Inej.
Changes: Not sure here. I know that since there's no undead in the setting, Turning goes WAY away, as well as their ability to trade spells for healing. I'm thinking that clerics lose most spells, and just use domains of their deity. But I'm really unsure of how to balance it. All classes are getting depowered, barring one or two, but this one is problematic. Also, what domains would the big four be, anyways? I want to avoid anything too broken. (And REALLY dislike summoning)

Ranger: A hunter from the fringes of society who prefers the company of animals to that of people.
Changes: Losing virtually all spellcasting. Just seems off-flavor. They may or may not get some bonuses (Bonus feats maybe?) to compensate. Possibly better movement.

Monk: People who believe the planet reveals something about their bodies and souls, and vice-a-versa. They meditate upon nature, attempting to learn the answers to whatever questions weigh upon their souls. They control the energy flow in their bodies in a mimicry of what they see in nature, gaining supernatural powers.
Change: Roughly the same. May add some Lay on Hands for spice.

Bard: Incredibly skilled musicians who have learnt to deal with political situations as well as entertaining. Their kind has adapted the teaching of monks and clerics to learn several tricks.
Changes: Removing their casting as is, and replacing it with various Spell-like abilities that they'll gain throughout their level progression, probably with choices and maybe a Combat-Track style choice or two. Trying to figure how to amp up their music (no pun intended) as well.

Fighter: Same. Maybe some spicing up if they need it, but I think that a flat fighter is around the power level I'm aiming for.

Rogue: Same. POSSIBLY better movement.

Paladin: Removed, due to the fact that religious crusaders don't have much of a role. I'm trying to think of a heat/cold based variant for devout followers of Ignis/Inej, but the code of conduct keeps saying "Can't travel with hot people/Can't travel with cool people" or such, and that just doesn't make me happy. Smite Feverish/Chilly?

Barbarian: An unfortunate soul that has somehow received a shard of the void inside their body. Due to this, they live much shorter lives and are prone to uncontrolable rages, although their strength grows to superhuman ammounts.
Changes: Lose Trap sense, and probably lose the Illiteracy as well. Gains a +2 bonus to strength over the level progression. If the shard is removed, they fall like a Paladin, losing Rage and most abilities until it's placed in them once more.

Well, that's most of it, I think. Most of these changes are very tentative, though. I'm fond of the Druid idea and the Sorceror idea, but there is some serious work needed on the Cleric to balance it out. Any opinions or ideas or suggestions are appreciated.