LaniusShrike
Smash Champion
The Mii's saving grace would be if it was a customized character.
I do not view the Mii as any parallel to Wii Fit Trainer solely because of being part of the Wii series games. Miis are Miis; they're fricking EVERYWHERE. Wii Fit Trainer specifically represents Wii Fit.
While Villager covers the "random attack usage" motif (which had been done before through Mr. Game & Watch), Miis have more to work with because, again, they're EVERYWHERE.
That being said though, Mii as that one character that you essentially "make" seems very plausible. Especially since, going by what the leaker said, it is "your" Mii.
So like Mario Kart, I feel there may be something like a "Smash License" where you choose the Mii to represent it; that Mii is the one you play as by default. (Though, others that have been customized can be used as well through download; possibly part of that "level up and transfer" gimmick Sakurai mentioned last year.)
At least that's how I see the possibility.
Yeah, I agree with this all around (including the part about the Villager sharing G&W's shtick). The customizable option seems best, since the available gimmicks seem taken.
I like the concept of the Mii having a fairly generic standards moveset and then some heavily customizable specials and stats.
-You have points to spend in the character's speed, weight/size, power etc.
-You can individually assign the four specials to the Mii, taken from any character you've unlocked
-Assumed to not be tournament legal or balanced.
-Either be saved via player names (Smash License, essentially) or via each individual Mii.
It could be really fun to create as broken of a character as possible and throw them against your friends' broken characters.