I'm guessing the reason Toad was removed from the Gamecube version's playable roster is because the developers couldn't think of Power Shots for him and Toadette. It would've been nice to have them playable though.
Anyway, all I really want is a couple of new characters and hilarious trophy cut scenes.
Well hopefully they get an idea for Toad and Toadette this time if that was the case (Mario Sports Mix was pretty inventive for Toad, so maybe this could mark his return). I personally want to see the return of Toad, Baby Mario, and the additions of Toadette and Baby Luigi (these guys really deserved in). Birdo could also make its return as well.
And yes, I definitely want to see some more of those hilarious trophy cutscenes. Those were really funny, and gave many of the characters a lot more personality (even Mario!).