She has the moves, she has the style.
Just tone her down a bit on the swearing and stripping, and she wouldn't be that bad.
She can keep her character by throwing some weaker innuendo; it's not like Smash hasn't done so already. ("Mei Ling, Samus took her clothes off!" and "You know, I bet if I took off all this heavy gear, I could catch her...")
and it's not unlike anything done in Kid Icarus Uprising, which has a lot of these kind of jokes.
[COLLAPSE="Uprising quotes"]Palutena: I'm sensing treasure somewhere to your left.
Pit: How do you know that?
Palutena: From the heavens, I can see through your laurel crown to divine your surroundings!
Pit: Really? That's amazing!
Palutena: And that's not all I can see, Pit. I can also see what's in your heart.
Pit: Oh... (nervous) Heh heh... That's really... something.
Palutena: So you'd better not be thinking about anything... NAUGHTY.
Pit: WHAT?! HOW DID YOU—
Palutena: Just kidding! Seriously, reading hearts through laurel crowns?
Pit: I know... I was... also kidding.
Palutena: (teasingly) Sure you were. [/COLLAPSE]
Bayonetta just needs to be toned down a little, just like Snake in Brawl, and she wouldn't fit bad. Bayonetta 2 being a Wii U exclusive and published by Nintendo definitely helps and could be a form of advertising in SSB4, even if by that time Bayonetta 2 wouldn't be as new, but could be enough to get more people interested. of course, another factor would be how well Bayonetta 2 will sell...