I think the general consnsus is that it will probably be banned from tournament play and that it can probably be turned off either in the items menu or from its own seperate switch. This is probably true in my opinion, but its too bad that those cool moves have to go to waste.
Thats the thing I hate about tournament play, always no items, sure you can give me that luck crap and relate it to Evasion and OHKO in Pokemon, but in a game so focused in on items it kind of kills it. Sure they can have 2 tournaments, one with items one without, but I don't ever see that happening because despite tons of people I know being better with items than without, the tournament scene is filled with those purists who don't want items.
Zero Suit Samus doesn't really count IMO (Sorta like Sheik or whatever it's called).
No body knows what ZSS is going to be like, while Ridley will be cool, Metroid isn't very ripe with characters that are noticable and can actually fight per say in this game, either they are super minor characters or just don't fit into a game like this.
I don't recall Captain Falcon using any of those fancy specials in F-Zero.
I also don't recall Captain Falcon ever getting out of his ship, thus they have some creative freedom with the character, but with someone like Kirby, Mario, and other platforming/adventure characters they have something to build off of, but still remain 100% loyal to the character. Falcon had to be built from scratch and even then he just punches and kicks, like you expect any normal human being to do.
I'm pretty sure they said somewhere that the original cast was returning, no matter who or what
I'll bet against you, the roster was already large, but also filled with gimmicks, Pichu for one will not be staying, Young Link might make way for another Zelda character, just 2 right there, and I'm sure there will be more to go.
If the past two games are any indication, probably not. The original was RBY only, Melee had only up to GSC, if the pattern continues we'll only be up to RSE Pokemon.
Melee came out in 2001, Ruby came out in 2003, the argument is moot, the games didn't exist yet to be a part of Melee, Diamond however has been out for some time and I'm sure they worked together on creating a good character from Diamond. That said I expect some changes to the Pokemon roster. Pikachu is the only sure-fire keeper, I can imagine Mewtwo, Jigglypuff, and Pichu departing for a better GSC Pokemon, a new RS Pokemon and a new D/P Pokemon. Lucario is a major player in the D/P race as he was one of the first revealed and has the ability to make a grea B moveset. RS could be either Blaziken or Deoxys as those have been popular choices, GSC is the toughest and might be skipped altogether.
I don't have my heart set on any characters I would like to see but there are a few I would like to see, Olimar is oen that comes to mind.