Question Character Customization best practices?

I dunno if this is the best place to ask, but the question doesn't really fit well in other categories.

anyway, I'm trying to make a character customizer for a game project, and I'm looking for some advice.

I already figured out blendshapes and made a functional prototype with a few basic sliders (nose, chin) that work, but this is only the beginning, since I have to figure out how to handle some special cases.
ATM I have a single solid mesh, but if I want to make it truly customizable (adding different non-human parts) I need more.

Things like a tail or horns seem simple enough - they can be separate objects that I just attach to the armature, but what about things that need their own blendhsapes on them. Things that cannot be attached to just one bone.

Lets say I want cat ears or bunny ears. The only method I can figure out is to cut off the ears and model several different ears, all with their own blendshapes. Might not be the best example, since ears would be mapped to just a single bone, so technically hey can also be just a single object. But lets say I want harpy arm wings or a giant, mutated arm or something. Am I correct in assuming that I can split the body into pieces and export each peace with the skeleton, and all the parts will work when put together?
Example: bare feet mesh, boots mesh, plate armor boots mesh, etc..

furthermore, for performance reasons, simply having all parts on the parent character as inactive and only activating the ones I need would work, but would it be better if I move all the parts to prefabs and simply instantiate the ones I need? Would it work? If I exported parts with a skeleton would I need an anchor or would he target transform be enough?


And the issue of size... obviously this cannot be handeled trough blenshapes, but I guess simply object scaling the character object itself would work?

And if I add options for fat/muscle on different bodyparts, how do assure hey "fit" if I split the mesh. If I made he upper arm really muscular and fat and lower arm thin, the verticies on their connection point might not match.


Anyone have any good advice or tips?


EDIT:
A though - what if instead of using blendshapes, I skin the mesh to extra "free" bones that follow the main skeleton? Wouldn't scaling and moving those bones have he same effect as a blendshape?