Mii's would be so fun to use, but i have no idea how their move set would work.
Most likely taking elements from Wii sports and Wii play. Heavy focous on boxing moves for A game.
B game...
Up and B: Alein upduction - an Alien craft lifts them upwards (from WiiPlay's Duck Hunt game)
Forward and B: Bowling ball, a hard hitting but slow moving projectile that follows the ground. Makes bowling noise instead of regualr contact noise.
Stationary B: Tennis Racket - deflector move
Down and B: Golf swing. A light damager but fast moving attack, can be adjusted by holding down the B button.
FS: Mii Parade! Summons a swarm of mii's from the system's mii list to run around causing damage.