Unlike Diglett's legs, the Anime seems to be trying to gradually show us Mimikyu without it's cloth, even though the game doesn't. I'll be surpriesd if this doesn't reach a conclusion.
I agree. I think part of Mimikyu's story could be that once you get it happy enough and maybe something more too, it can be "confident" in the world, making it change forms. Maybe it's just never been done? I personally think Mimikyu's thing is confidence issues, not the fact is just disguises itself. But that's for people to take for themselves.