Just wanted to confirm some things I said earlier:
Model replacements only change one costume each. It's stored in the file with all the textures--that's why when people tried to use Captain Jim's "Metal Sonic" (a R.O.B. texture) on Sonic, what they got was a very glitchy (but freeze-free) R.O.B. with Sonic's moves. That's why you can use a Pikachu texture with no hat on the other slots and the headgear does not appear. I haven't done it but I assume putting a Wario with a jacket in slots 7-12 (overalls) would give you a jacket Wario.
Yes, the model must conform to the skeleton (tells it how to move) and hitboxes (tells it what part can take damage or deal damage at a given time), so I can't make an accurately tall Mike Jones with Ness's moves.
Also, Link's bombs, arrows and boomerang are not part of the individual costume slots. If I wanted to edit those they'd all change. No exploding torces, no baseballs, no magical yo-yo. His sword and shield, however, can be changed. Mike Link will have to have bombs, a boomerang, a bow and arrows, a bat and one of those mirrors from the later dungeons. Still, Link's stance is not so different from Mike's. Mike has never had a voice actor, so that won't feel so weird. I'll do the best I can when I finally make this.
Vile's got some awesome ideas himself. I can't wait to see some of them.