I'll concentrate on a class which assumes animal forms, perhaps with vermininous, hybrid, or swarm forms as options later on. Larger, smaller, aerial and aquatic forms or abilities will fill in the middle levels.
Good idea, but what about making each of those a separate sub-specialty? IOW, someone who masters regular animal forms, someone who masters swarms, etc. Its a little more work, but the benefits could be worth it.
I'm not clear as to what you mean by "hybrid"- is that hybrid (aka magical) beasts? Or is that a Skinchanger who can't do a complete change, but only mixes human form with animal simultaneously- a quasi-lycanthrope?
"Skinchanger" still works as a name.
Agreed, for the very things you mentioned.
As suggested, change hit die to d12. Ranged combat options will be almost nonexistent. This will be a frontline scrapper.
Good.
Change class skills to 4 + Int Modifier and shorten class skill list. Class abilities should supplement this where appropriate.
Looks good- probably a similar list to the "nature-boy" classes would be in order. Or, if you have the time, check out what kind of skill sets you find in the fuzzy monsters from the various MMs.
Cleric/Rogue BAB should be fine, with potential bonuses to Strength and perhaps a scaling enhancement bonus to natural weapon attacks granted by the class.
Agreed.
Fort save should be good. Maybe Reflex too.
I think that both of those saves should be good. Leave the Will save as the weak point...their animal nature, repressed and controlled in most of us, wars with the higher minds in those who practice this art, leaving them vulnerable.
Limit proficiencies to simple weapons and light armor?
Absolutely.
In hindsight, I'm thinking the simplest (but still somewhat flexible approach) would be to have most or all of the powers granted by the class come in the form of at-will abilities, similar to a Warlock's Invocations.
That makes sense. Despite the crazy fluff of the class, it is, at its heart, a melee class. If it helps, think of it as sort of a Barbarian (the HD & ferocity) with a touch of Ranger or Scout (stealthiness & subtlety) and the Druid (shapechanging, natch).
The lowest level powers would provide skill bonuses or things like lowlight vision or resistance to temperature extremes. The next tier would represent basic forms, with one selection available to a 1st level character. Two higher tiers would represent higher level options. What to call the 'levels'? Or the 'powers' themselves?
You might want to peek at the geomancer PrCl for some ideas.
Personally, I'm thinking low-light or darkvision should be a standard 1st level power for Skinwalkers- double range if they already have that benefit from another race or class.
Other benefits you might want to base on the particular kind of animal forms the Skinwalker learn.
Overall, as a potential GM, my personal take on this class is that I'd be more comfortable with the class if there were a clear tradeoff in its abilities between power and flexibility.
(I'm just throwing this out there...)
IOW, I could see one Skinwalker mastering many forms, but none of them are particularly powerful, whereas another might master a single form, but be able to improve on it constantly. Yet another might be a master of verminous swarms.
The first might have no form bigger than his natural size, some of which could swim, others could fly, some of which could burrow, one of which might regenerate (slowly).
The second might have a single (probably predatory) creature as his basic form- perhaps equivalent to a "juvenile." Eventually, he could become the equivalent of an "adult." Then he might be able to add in things we think of as templates- Feral, for instance, then Dire.
The third would start off with a number of creatures in its swarm equivalent to his HD (or something), with the swarm growing in size over time. Because of the relative power of his creature form, perhaps, like the first kind of skinwalker, he can master a few different kinds of vermin forms, and perhaps, like the second kind, he can improve his verminous swarms with templates.
Another thought- perhaps this class has options that only open up with multiclassing.
For instance, a Skinwalker with divine caster levels could choose to add Fiendish or Celestial elements to their forms, depending upon their alignment.
(OTOH, this might also be something for a shapechanging PrCl.)