Speaking for myself I personally thought that the "reversals in MKDA were too slow to have any sort of impact on the game. What I mean by this is that by the time you managed to actually perform a reversal you were so sick of the attempt it just seemed useless to do it anymore. My idea is to employ more of a counter in MK6, by this I mean that there could be a preselected button for all characters that could be used to rather than block or reverse could be tapped when about to be struck to avoid the attack or counter with an attack of their own. I know this may sound a bit confusing so I'll provide a few examples.

Jax counter.
Opponent kicks or punches at Jax, as the attack is about to land, press R button (not necissarily real button) and Jax grabs the opponents limb and without hesitation spins them around before tossing them across the arena.

Kitana dodge.
Opponent kicks or punches at Kitana, as the attack is about to land, press R button and Kitana does a back handspring to avoid the attack and gain distance from the opponent.

Reptile reversal.
Opponent kicks or punches at Reptile, as the attack is about to land, press R button and Reptile grabs the limb and breaks it, he then runs up thier body and does a sumersault kick knocking them down.

Now for the system to work it could work on the same premise as the Lord of the Rings parry system, the button can be continually pushed to avoid attack but in order to avoid overuse there could be a meter very similar to the run meter (not necissarliy displayed, but shown by fighters fatigue, ie. hunched over, out of breath.) When this happens the next time they attempt to avoid an attack they will fail and it will cost them dearly. Double damage due to the fact that they're already quite a bit weaker than normal.

I apologize for the long message but it was the only way i could explain it. Hope you all like the idea and if you have any ideas on characters reversals of your own, I'd like to here them.