i was told their was something in AUM 40:

pixel_for_bmap and pixel_to_bmap.

ok so you have to make a pretty darn uv skin, and hardcode every pixel for every part. but this way you could do it i think

I am almost certain that is not the way it is done it professional games. I noticed that in morrowind it is very clear (to me) that the head, hair, armour and clothing are seperate objects and it would be possible to use an external modeller(Blender, for example) to give the same bones animation to many different clothes and armour, so they would perfectly fit around the player. As for the changing of type of clothes, face, etc. it is the same model, just with a different texture. It's not easy, certainly, but that is what making an RPG would involve.

I think helmet, armour, shoes, weapon etc are different models attached to player's vertex with same animation. So you don't have to change skins just models. Only base looking (naked or skeleton) human still the same. Then you may attach different shaders to different part of armour too