Modifying feats from dragon to humanoid

[Malapterus]

I want to modify the following feats so they trigger against Humanoids & Monstrous Humanoids, instead of dragons:

Dragonfoe
Dragonbane
Dragondoom

I know these working on dragons is kind of balanced against the fact that dragons are ostensibly rare (I mean if you're taking all these feats you're probably in a dragon slaying campaign but still) and have lots of armor and HP compared to most creatures, while humanoids and monstrous humanoids are both common and comparatively weak.

How can I modify them to make them fair for use on an evil PC-level NPC?

[Kayblis]

Yes, you can. The same way you can make a custom "humanoid-bane" weapon property and get +2/+2d6 against virtually everyone in your campaign and every single PC would be actively gimping themselves by not picking it up as soon as possible.

There are other ways to do this. If you want a "humanoid hunter"(literally any murderer you can think of, that's not special), you can make a Ranger with all-encompassing Favored Enemy. Or just a character two levels higher. If it's an NPC, you don't even have to follow hard rules and most of what you want is given by common items anyway.
-Dragonfoe is the general effect of being 2 levels above your own and +4 to your casting stat.
-Dragonbane is a weaker +2 Bane weapon.
-Kaorti Resin gives any weapon a crit modifier of x4.

[Malapterus]

Yes, you can. The same way you can make a custom "humanoid-bane" weapon property and get +2/+2d6 against virtually everyone in your campaign and every single PC would be actively gimping themselves by not picking it up as soon as possible.

There are other ways to do this. If you want a "humanoid hunter"(literally any murderer you can think of, that's not special), you can make a Ranger with all-encompassing Favored Enemy. Or just a character two levels higher. If it's an NPC, you don't even have to follow hard rules and most of what you want is given by common items anyway.
-Dragonfoe is the general effect of being 2 levels above your own and +4 to your casting stat.
-Dragonbane is a weaker +2 Bane weapon.
-Kaorti Resin gives any weapon a crit modifier of x4.

It's for the most evil member of my evil party; a Drow vampire who wields a scythe. I have so much I want for her:

Reach
Barbarian-style Rage
Silent movement that ignores minor terrain nonsense like caltrops or ice or 'wait this is water' (gliding along instead of walking like the cool vampires do)
Increased threat range on that scythe
Increased crit multiplier on that scythe - really looking at that 7x from dragondoom.

She's supposed to be a power attack/great cleave type who gleefully reaps through crowds of foes and can burst out some extra power against more serious opponents.

The 'Reach' problem is possibly solvable by reskinning a weapon; adding variable reach to a scythe gives it basically the same properties as a Spiked Chain; swapping out the weapon finesse for that x4 critical could give me a reasonably balanced exotic 'Greatscythe' or 'War Scythe' so I just have to blow a feat.

Just making her Barbarian after her LA would give her the rage, plus full BAB & movement speed & evasion, even though fluff-wise she would not be a barbarian. The DR is a waste because she already has it from her template.

I'm not sure about the gliding thing; I'm sure it's important enough to charge her for but I don't want it to be an item, just a spooky supernatural aspect of what she is.

The threat range thing, I don't even know. Maybe porting Dispater over, making it about adamantine? I really don't want anyone adding triple-crit to a scimitar, maybe I could have it go up one point at a time.

The increased multiplier would be more than covered by this tweak of the three feats, but it's not horribly important. x4 is a lot.

The scythe itself is Adamantine with the Vicious enhancement and a built-in 'precise strike' effect (I like to picture it cleaving through unimportant background items to get to its target). Because it's Adamantine I do not think I can use Kaori Resin, but it already has a 4x crit so that's kind of a lost cause.

Maybe I should try to piece together the things I like from Barbarian, Ranger, Fighter, Hexblade, and War Hulk and try to balance it out using ClassCalc.

Ranger: Convert 'favored enemy' into a pre-set thing that affects all humanoids & monstrous humanoids. Replace the fighting style feats with something to benefit the crits, or maybe with the Weapon Focus tree. No need for animal companion or ranger spells.

Barbarian: Just the Rage; again, maybe it can only be triggered when attacking humanoids and mumanoids.

Fighter: The need for bonus feats provided by Fighter may be negated by the one provided by the ranger mod.

Hexblade: Maybe just a couple of spells in your pocket.

'Reaper of Men' or 'Manslayer' or some such. Maybe make being undead or otherwise unnatural one of the prerequisites, although I am seeing this as a base class.

War Hulk: Area-of-Effect melee attacks, woo!

[Kayblis]

Well, now that we know why you want the feats and extras, we can work towards it. You're making an anime character, and for that there's no better book than the book of Anime Fightan' Magic(Tome of Battle: The Book of Nine Swords).

This book introduces maneuvers(abilities to activate as a swift/standard/full-round action) and stances(on/off passives you can have, one at a time, swift action to activate or change). It also introduces "initiator classes", which are maneuver users with progressions kinda like spellcasting(9 levels of abilities, unlocking a new level each odd initiator level). The fun trick here, though, is that your Initiator level is equal to your initiator class level PLUS one-half the other non-initiator levels you have, so a Fighter 8/Warblade 1 has a Warblade Initiator level of 5 and can pick up to 3rd level maneuvers and stances in its first level. This book is great for dips.

A couple of maneuvers do what you want to do with your character - Stone Dragon maneuvers include a couple of "deal +Xd6 damage, ignore DR and Hardness", and there's a Shadow Hand stance(Step of the Dancing Moth) that lets the character walk on any horizontal surface, ignoring difficult terrain and being able to walk even on water. A more feral, rage-like combat style exists in the Tiger Claw school, which includes crit-based maneuvers and leaping attacks. There are maneuvers that let you roll Concentration instead of a save, and others that let you block an attack with your own attack roll instead of your AC. It's a huge variety of abilities. Your concept seems to fit very well into the Tiger Claw and Shadow Hand schools.

All in all, the Warblade from this book is what the fighter should have been like. The base classes and PrCs here are stronger than the average martial classes in the PHB, and are still weaker than full casters. You start combat with all your maneuvers readied and can refresh the ones you spend in different depending on your class. This is not a spell system, but it's different from how martial classes are used to play.