You guys are missing the point with the unique playstyle thing. Geno is a third party character, and is relatively obscure compared to the ones we have. He isn't going to be in the game. However, he would certainly be cool to play as I would think. But the 3rd party issues are pretty much holding him back, and will continue to hold him back.
The playstyle in question needs to make sense with the character. Robin's playstyle makes sense. It's nifty because it basically embodies Fire Emblem based on the concept of breaking/losing weapons. However, on the fighting game side of it, he's essentially a risk reward character with his exchange of the Levin Sword and Magic. That's what I'm talking about with gameplay. Not what they use, but what kind of moveset they would have.
The popularity of a series might have mattered a whole bunch in previous Smash titles, but this isn't Brawl anymore. Clearly. There were plenty of big characters they needed to add, like Wario and Diddy Kong. Those are essential characters. There are hardly any "essential" characters left. So gameplay is what drives these characters for the most part.
It's really not a hard concept. What makes this character different? What can they do that nobody else can? What would make somebody want to play as this character? Pretty much all of those characters revealed so far have something awesome coming with them. Something that a lot of the rest of the roster doesn't have. That's what got Rosalina, Greninja, and arguably Wii Fit Trainer in the game as it is.
I digress. I get the vibe nobody is going to read or listen to this because of the precious sales that absolutely don't matter. Or the idea that Sakurai thinks a character should get in to represent a game.
"Oh wow! That game sold well! Let's add a character just because of that!" No. That's not going to happen.
"Wow. I like that game. Let's add a character to represent this one game." No. That won't happen either.
Before you say Sheik, she was added because of gameplay. The transformation gimmick was a great idea (that didn't work very well). Sheik is probably safe now due to nostalgia as it is.
Bottom line is, that a character has to have something unique going for them, and it has to make sense for them to be added. Arbitrary reasons like the ones that are thrown around all the time are not really as important as people make them out to be.
Take it for what you will. But that's my stance on the topic.