Earlier I stated that combo/button inputs make more sense, to me, to stay as a Ryu trait.
But I will say that I think it has one use for Mortal Kombat characters: the fatality.
Of course, Finishing moves are a staple of Mortal Kombat, and this would almost certainly be the Final Smash.
For a potential Scorpion/Subzero, I think each should get three final smashes- and that the ability to choose between the three is one of their special traits.
You have a Fatality, a Friendship, and a Brutality.
The button combo in some way dictates which is done.
If this is needed to be balanced, the moves could just be cosmetic differences (different cinematic sequences for each, with the same result).
Weirdly enough, I'd say Bayonetta 'fits' better than Cloud or Ryu to Smash.
Her personality and attack are so over the top and pronounced that, seeing her with goofy Nintendo characters doesn't feel weird as it should be.
I just look at her and think, "It should have been Lara Croft! Especially the nonstop bullets."
(sidenote: I own the bayonetta dual pack... but why can I not seem to stick with playing? I think I need to put it on the TV and not handheld mode).
It'd be all the specials though. And they'd all be unique specials
I edited my post above-
I dont think the specials would be that unique. For example, Scorpion's spear, while the animation is different, would function the same as Link's boomerang.
And it would be really funny to see Ice Climbers and Sub Zero share a move.
Mortal Kombat, even if full of gore, is full of camp.