Joint/Weld Constraints on a Mesh?

Say I imported a mesh from blender and put it on a part. After that, I want to be able to add more parts to the mesh and animate them. Is this something I would be able to do, or would the joint and weld constraints not work?

The X-Y Problem
(Are you trying to do something more specific?)

I think you would only need joint constraints, no welds.