Are details allowed?
All for one, and one for all.
Smash should work to attain the goal that so many other fighting games do not -- bring back all its prior contenders. Melee was awesome for having the entire 64 roster; it was somewhat nostalgic, mixed with a modern feel. But then Brawl came out, and the series, to me, turned into "just another fighting series".
I have a strong resentment towards Brawl not because it changed the fighting formula... but because it scrapped fighters. Now I could care less if any of the Brawl newbies got cut... The irony. I feel I couldn't choose a main, because in the back of my mind, I thought, "What if this character I'm attaching myself to... doesn't make it back?" It's a horrible feeling, that such an iconic character means NOTHING in the hands of the developers. To them, its just a model with textures that people'll pay money to play. But to me, it means so much more than that.
Young Link.
The clone thing is BS; this character represents OCARINA OF TIME, hailed to be one of the greatest games made. Give the guy some bombchus! The Megaton Hammer! Hell, what's wrong with giving him a few masks? I'd love to see me some Fierce Deity through this guy. He'd be changed... but he'd still represent the same thing. (No offense, Toon Link, Wind Waker's my favorite Zelda title... but I'm just not into the fighter representing it.)
Pichu.
2nd Gen. That in itself should warrant something. According to so many polls I've seen (including one here!), the 2nd Gen's generally the fan favorite generation out of all existing four. Pichu represents the most popular Pokemon generation, and I HIGHLY doubt there's anyone else in that Gen lineup that comes remotely CLOSE to its iconic status. Sure, Pichu was a clone, but perhaps... I dunno... Pichu should take some advice from characters like Luigi? You know, lose that clone status a bit? I doubt that'd be hard. And hurting itself... I always thought that was kinda cool, how it stayed true to its Pokedex entries of old. Made for a really challenging character to play. Respect to those who can tame this sucker.
Roy.
He's our boy. While his Fire Emblem character may not be the best (matter of fact, it's claimed to be one of the worst/hardest Lords), he's become apart of Smash history -- without him, and Marth, Fire Emblem would've never seen shores outside Japan, let alone be as popular as it was. Roy's a piece of FE history... And be honest, if all you saw was Marth on the roster to rep FE... top tier or not, I don't think I'd take FE that seriously.

Blue hair + red hair > blue hair + blue hair.
Dr. Mario.
Hmm, he's a bit tougher. His games are good, and they're still coming out strong, but does it warrant a separate playable character...? Don't get me wrong, I love me some Doc; he's an old main for me, and I love his easier-to-KO playstyle when compared to Mario... made for a nice contrast. But with the possibility of alternate costumes... it's now really hard to defend him. Either way, whether he makes it as a costume, or a fully separate playable character (give him his own faction, a rep of the puzzle-game faction or something)... I'm looking forward to seeing an incarnation return.
Mewtwo.
THE prime example, and why my fears for cut characters have no limits. He was no clone. He was original. Granted, his moveset in Melee isn't exactly the best, but he's STILL a popular CHARACTER. Maybe not a popular fighter... but definitely a popular character. Nowadays, all I see is GAME FREAK whoring the hell out of Mewtwo, putting him in more games, or featuring him as a prominent face
among other Pkmn. Ignorant *******s. I feel I'm being slapped every time I see it. Get him back in the ****ing series already. *******es.