i dont know if it works just for a spesific group of model but you can change the skin by

my.skin=2; or something but i think this will change the skin of whole model.

You may try making hands,torso etc. spare models but its harder to bring things together and keep them there. And it doesnt look good.

i wonder this too if its possible to change only a group's skin not the whole model.?

(maybe my.group1.skin ? i dont think so but..)