assemble a robot with many different sub-model

hi,all. I want to assemble a robot with many sub-model : head ,leg ,body, hand, weapon. And these sub-model can be chosen. then, my robot can have different head,body,weapon etc. By unity3d,how can I attach the sub-model to each other and how play the animation will be ok.

 

If i want to play a walk.should i just let the every sub model of robot to play the walk by itself. and by attach (with transform.parent = ),the robot will be looks like walking?

 

Late reply.
Non coding artist response.
You can skin separate mesh objects using the same skin in your modeling package. Export everything together and in Unity each separate mesh - skinned together to form a complete robot - will be treated as separate objects in Unity with separate skin mesh renders. These can be turned on/off to your desire.
Not sure if this is the best approach - but it is a workable solution.
There are probably better code workflows that accomplish this task more efficiently.