Obviously, he is a fan of II Piantissimo and thinks it would be cool if he were in Brawl.
I can say the same thing about Waluigi. It'd be awesome if Waluigi was in Brawl (my opinion), but I don't know what kind of attacks he'd have either.
Example: We're not sure of Mario's capabilities in this new game, but we still think it's awesome that he's participating.
(Hope I don't sound rude or anything)