Mechanically, which genre's would you like to see crossover with Smash next? I'll gladly shill for more fighting game and platformer characters, but I'm curious as to how a puzzle game character could bring their mechanics into Smash, hopefully without feeling awkward. I think Hero, Pokemon Trainer and Robin do the whole RPG thing pretty well. We do have Dr. Mario, but he's obviously an off-shoot of an existing character.
And that's not even getting into character/franchise specific stuff either.
Rail Shooter
I know Star Fox already represents the genre... but at the same time it doesn't?
Back in Smash 64, characters were given movesets to be basic fighters, using no gimmicks at all. But as more smash games came, Sakurai has been attempting to make characters play more accordingly to their genres.
Which is why I would love a rail shooter character to be included TODAY.
Saki Amamiya from Sin & Punishment would represent this genre amazingly.
All I ask for is that his Neutral B spawns a big red crosshair (color depends on the player) in the middle of the screen, and that's the direction where he's firing bullets (Bayo style). Then with the joystick, you can move the crosshair around, and Saki's aim will fire accordingly.
Now obviously this means Saki can't move... with the joystick at least. While he's firing, joystick is used to move his aim around, and L+R are now used to move Saki left or right. Double tapping will make him roll.
Just take a look at the only 2D sidescrolling stage from the entire game, to get a hint of how it would translate into Smash.
FPS
Long overdue. But yeah, Doom should be the one to represent it. It just makes sense (to me).
Haven't thought much about his mechanics, but at least having B (left/right/up/down/neutral) cycle through his weapons to use for regular attacks.
He'd be ammo based, and everytime he hits an opponent from up close, he recharges ammo.
For recovery I can think of two things. 1) Rocket Launcher downwards. And 2) "Random teleport trap" like the ones you never see coming in the original Doom games.
Also, if Doom Slayer could plant one of those exploding barrels from out of nowhere, it'd be a huge huge plus.
Beat 'em Up
Nothing really that stands out, I guess. Smash itself lends itself as a sort of beat em up type of game (except with platforming) so there's nothing really special that this genre could bring to the table, other than just watch characters of one of my favorite game genres fight, of course.