For me, I would like Jade's amplified rang to connect on block, allowing her to actually take advantage of the plus frames. I'd like to see some counterplay added to Kabal in the way of flawless-blockable gaps or some of his tools being made slightly less safe. I'd like Lao and Jax to be deleted from online play. And this is certainly wishful thinking, but I'd like the window to tech throws to be increased for online play, possibly based on the amount of ping. Too many times I'll know a throw is a coming and be ready to tech, but by the time the animation comes out, it's already too late.
I also wouldn't mind a bit more damage scaling, especially for Fatal Blow kombos and unbreakable kombos. Losing a match because you made one mistake that cost you 50% of your healthbar is just not fun or exciting.
The only other big change I can think of is to reduce the downtime between matches. I feel like I spend as much time looking at menus and useless currency updates as I do playing the game.
Oh yeah, and remove variable frames on block or hit.
Oh, and make Shao Kahn playable. I wouldn't be against a total character overhaul for him. He's just a turd of a character right now.
Damn, I keep thinking of more. Make some of the useless variations usable, like Spawn's gun variation. It's easy to see what specials and overall variations are underperforming. I'd like to see these variations and specials buffed before the overpowered variations and specials are nerfed, honestly.