Yeah, I think Wario should be a playable character in SSBM. That would be so neat. Wario would finally get the chance to smash his big yellow elbow in Mario's face. He's been in all the other games where the gang is together (i.e. Mario Party 1, 2 & 3 as well as Mario Golf & Mario Tenis) so why not?
Go Wario!
"Fate has no forgiveness for those who dare stand against it"