Idea:
Mario is replaced with Jumpman, and despite the name he can only jump his own height, and dies when he falls from any height higher.
Weegee.
Bowser is... yeah... his down special is the same as Wario's and he's WAY slower and can't jump as high, heavier than even Master Hand.
Wario is dead the entire match and can't be interacted with, his costumes are also stages of decomposition so you can 'play' as wario's skeleton.
Sans is Ness.
Megamind is the only decent option.
Incredible Gassy is just Wario.
Goku might also be decent.
Same for everyone else.