Model notes: My model predicts 1.66 slots and 2.22 move sets... which is a little strange. I take that to mean Metroid probably deserves another slot, but maybe not as much as you'd think since ZSS is a separate move set. I'd boost the chances for Metroid a little higher due to the very high demand for Ridley, so I'd go on the high end of that. But that's pretty much all Ridley, not a lot of room for Dark Samus.
That's one of the shortcomings of statistics, Erimir. They're very useful things, and I'm very glad that you're putting them to use here, but they can't account for EVERYTHING. Metroid hasn't sold particularly great, but it has some things up its sleeve that kind of throw off your calculations. First of all, it's a
critically acclaimed series. Super Metroid and Metroid Prime are pretty regular customers on "Top 50 Games of All Time" lists; other games in the series are also noted for quality. While critical acclaim isn't anywhere near as important as sales, it does need to be considered.
Another thing that needs to be considered is the cultural impact Metrioid has. It's impossible to measure cultural impact on any mathematical model. Let me just put it this way: Mario, Pokemon, Wii, DK, and Zelda are leagues apart from any other Nintendo series in terms of both impact and sales, but I'd make the case that Metroid takes sixth place in impact (it's in competition with Kirby, methinks). You see pixelated Metroids in places you'd never expect, and most people seem to recognize Samus (and a good many know her gender). I do concede that it may have less of an impact in Japan, but the developers are certainly aware that it's a big deal here in the West, bigger perhaps than its sales imply.
There's also the fact that the franchise considerable overlap with the "core" Smash community, and the very nature of the Metroid characters appeals to the casual community ("Oh boy, mommy, I want to play as this big dragon. He can take Bowser down, I'm sure of it!"). Now, I'd say it would make more sense to introduce a Metroid character than one from something like Fire Emblem or Mother; the nature of the characters available make them more likely to be hits. A casual is probable to like a cool guy with a sword or a cute little magic boy, but I'd say they'd gravitate even moreso to the giant purple dragon.
Now, please don't take me for a Metroid fanboy; I'm anything but that. When I was a lad, I played and vaguely enjoyed the first two Prime games, but I didn't consider them anything special (I obviously have to go back and play them again now that I'm older). Metroid Fusion and Super Metroid were great games, as was the original, but they're FAR from my favorites of all time. Noneteheless, I see the cultural impact of the series and I note that another character is fitting; I think Ridley would be amazing to play as, so I'm supporting him.
Long rant aside...
Dark Samus: 5%
She's in THIRD place as far as Metroid newcomers go. Ridley is the obvious favorite and the only one I really think has a solid chance to make the cut. That said, I'd place Adam Malkovitch above Dark Samus. He has both relevance and seniority over Dark Samus; everything Metroid that we've seen so far has been Other M, too. I don't know why Sakurai would choose Dark Samus. She could have potential and is pretty well liked, but really... her support pales in comparison to a certain other enemy and she's not exactly a series icon. I just don't see it happening... Ridley or bust, with maybe a hint of Adam Malkovitch sprinkled in.
Dark Samus Want: 33%
I wouldn't say no, but I certainly wouldn't be saying yes. Her chances are pretty much mutually exclusive with those of my number two character, Ridley, so.... Also take into account that she'd share a lot of similarities with Samus, but at least she'd have a good amount of potential for uniqueness. All in all, a decent character that would be somewhat fun to play as, but... this work could have been put to a better cause.
Doctor Mario: 2.46%
The reveal of alternate costumes killed off his chance of a separate slot. Most people think that, anyway.
Groose x5
DAY OVER
GROOSE IS BACK!