Something of a case of a character that should have been in Smash already, Ubisoft and Nintendo have been close collaborators since the Wii, and Rayman Origins and Rayman Legends were great games. Rayman may have had a poor start in gaming, but he has endured to headline some great games and has the perfect cartoon look and move set to fit in the Smash franchise. Also Globox as a clone character would be nice.
Simon (or any) Belmont
I never really got into the Castlevania series, but I have been enjoying the Netflix anime and recognise the importance of the franchise in gaming history. I imagine that a Belmont would be a heavier character with a diverse set of moves befitting the array of weapons that can be found and equipped in the games. God forbid they do another "Shadow Emissary", it would be cool to introduce Belmont tripping over Link as they both raid Ganon's Fortress. Belmont also opens up the option of an overpowered Dracula joining the roster at some stage.
For the N64 generation (like me) Rare's endless parade of 3D Platformers were a vital part of our childhoods and their departure from the scene is a little bit tragic. The return of Dixie Kong to the Donkey Kong franchise does bode well however, and if Nintendo and Rare can get their shit together, Banjo and Kazooie are much-needed on the Smash roster. Transforming Banjo, grenade eggs and golden feathers give the character (yes, they're one character, not two, in Smash terms) plenty of move options and maybe Grunty can join them down the track. Just please, don't put in Mambo, he reads as pretty damn racist, even with the pink, fuzzy feet.
Yeah, fucking Ridley, I'm sick of the stupid justifications for keeping him out of Smash, except as a level hazard. "He's too big!" cry the idiots. Well Kirby is only 8" tall and Ganondorf around 7', so clearly they don't stick to any damn scale. Ridley is an iconic villain and with all the damn Mario franchise characters clogging up Smash, we need another Metroid representative. Sure, he'd be big, but think like, King Dedede size, but lighter and quicker. Something like a less controllable Greninja. What you want Baby Mario or something else instead? Get real, nothing would be as cool as a giant, dinosaur, space pirate, cyborg.
Smash needs more girls and few Nintendo girls kick butt as hard as Dixie Kong. She rescued both Donkey and Diddy with help from a toddler and can fly with a flick of her pony tail, sounds like real Smash potential to me. As with Banjo and Kazooie above, she's made a comeback and should get the recognition she's long overdue. There's always room for more monkeys running around, jumping and flinging fruit-based weaponry.