I'm still waiting for universal air dashes.
My idea for changing up SSB's -Gameplay would be Jump-Smahes. It takes away your second jump and your character has problems to break the movement, but you get a speed boost for your jumps:
Smash-Jump on the floor:
Up:
Super-Jump (fast vertical jump like from Marvel vs. Capcom 2. You can't get higher, then the characters maximal jump-height).
Down:
Backflip (Mario's backflip from Donkey Kong '94 and Super Mario 64. Another counter move, since it comes out fast and you land close to your opponent)
Back/Forward:
Leap-Jump (fast forward-move with possible air-attacks close to the floor, but horrible downtime after landing and you can't attack in the first couple frames)
Smash-Jump in the air:
Up:
Vertical-Jump (a little higher and faster then a normal jump, but almost no air-control)
Down:
Meteor-Drop (very fast fall, but defenseless the first couple frames, almost no air-control and a longer downtime, if you're close to the ground)
Forward:
Air-Dash (fast forward-move, but you can't attack in the first couple frames, very linear movement and very predictable)
Back:
Air-Escape (fast backward-movement and can be easily aimed into a direction, but you can't attack in the first couple frames and you travel not very far. It's almost like Melee's Air-Doge).
But i think it is too complex for SSB and would be an option for an Smash-Clone.