A dark, twisted Bowser would be awesome.
Ganondorf or a Ganondorf armor set for Shao Kahn would be cool.
Ridley is already pretty menacing and would fit in well.
I could see one of those characters possibly making it as a Nintendo Switch exclusive. Someone like Link, though really a fun prospect, might not have as great as a chance. We’ll see soon enough!
(And in addition to this, I’d be stoked to see Scorpion, Sub Zero, or Raiden make it into SSBU.)