Cool! I’d repeat Sam’s warning from the top of the thread, that making a full-fledged RPG in I7 is a lot of work. But I also think it’s a lot of fun to tinker with ambitious projects, and it’s not like I finish anything, so I’d hardly discourage you!
Layered clothing is pretty notoriously difficult to do. There’s some complicated code going around for it–see this and this extension from this thread. Good luck!