Unless someone changed it with upbge … You can’t rig a mesh in- game.
You can remove the deformed skin mesh, by unparenting, but you can’t add one. Even in Blender the rigging gets performed by the armature modifier. The parenting option is for backward compatibility only (it is not needed).
In other words: rigging is static.
But you can exchange the deformed skin mesh, by replacing the mesh (rather than the object). This way you can exchange cloths. The requirement is that there is a rigged skin mesh object already. This mesh does not need vertices. So it can be invisible. By the way you can load meshes dynamically via LibLoad.
see: How to: change a skin mesh
I know it is the opposite of what you want to achive, but that is what I can offer.