Can skinned avatars be assembled at run time?

I’ve been trying to build a character creator that would allow me to dynamically add/remove things like hair and armor.

I can make it work by making it all part of a single imported FBX and then hiding what I don’t want to show but that means carrying around a bunch of extra weight and that I have to update the whole model in order to add anything. Instead I’ve been trying to export the parts like the hair individually from maya and then attach them to the skin and bones base model at run time. But when i do, they don’t seem to render.

What are the issues around this and are there any examples of making something like this work?

See this:
http://forum.unity3d.com/threads/uma-unity-multipurpose-avatar-on-the-asset-store.219175/

http://uma.unity3d.com/wiki/index.php/Welcome

Its the solution that has emerged in the community as the defacto standard.