Mario characters, whilst I love Waluigi in a weird way and at first was disapointed he didn't make the Brawl Player Characters I can't see what he'd bring. When you've got Mario, Luigi and Wario who are all more iconic then Waluigi I don't see why another character should be denied for him. The same goes for Daisy being so much like Peach and all the Mario versions. I think that stuff would be better reflected in skins or something for characters.
I think the best Mario characters to add would either be Toad or Bowser jr.
Also I just remembered, Meowth in SSB4 anyone? He's certainly more recognised then Lucario.
Unlike the Adventure Mode in Melee, I always wanted an specific adventure mode for each character. Like I guess some would be similar stories, but the Boss would reflect the characters you choose. Mario/Luigi/Peach/Yoshi to face Bowser or...Giga Bowser? Fox for Android? Pikachu/Jigglypuff/Meowth for...Mewtwo/Lucario or maybe even....Arceus? (Mewtwo/Jigglypuff is in Brawl too right?) Link/Zelda for Gangdolf(idk how to spell his name lol)
That's just me dreaming though right? LOL