Skinned meshes with only Motor6D [Issue: meshparts not joining]

My game wants to swiftly transition from using normal custom rigs (without mesh deformation) to using skinned meshes. It is important that we retain a certain amount of mesh parts so that we can utilise old animations and assign accessories to specific locations of the rig, how would you accomplish this?

I’ve tried reimporting the model via the avatar importer and reassigning joints correctly, but to no avail. Each joint has a Motor6D in them with their name. It should work but I am not sure why it isn’t.

However, when I try and rotate the parts in the animation editor, nothing really happens.