This is sort of a four part idea I had about new ways they could take the fighting.

The first is my favorite, I call it "compound damage" because it would literally affect the characters depending upon their remaining life. This would be a great way to balance in slow but strong characters against very quick fighters (there aren't many cases of slow fighters in MK).

This is how it would work - double the health bar, with both being all white to begin with. At one hit, they both turn green until the bottom bar is done. Then it turns yellow and slight bruising or hesitant attacks show up, weakening your presence. Halfway, it turns orange and you begin bleeding in several places, further debilitated with speed and blocking effectiveness. Finally it sinks into red for the last quarter and your character looks jacked up with large weaknesses. This would give skilled players the chance to eradicate much weaker foes very quickly, but against equally skilled players you'd both have to end up battered. Also, with a very large or durable character, perhaps they lose less ability than small, quick characters. The first bar gives you a regular fight's worth of chance so I think it would be a very fair thing to add. And fights would be longer and more interesting.

The second idea is simply that they make certain characters have better avoidance techniques than others; perhaps a quicker fighter might be able to easily block an average movement fighter at the beginning of his combo, but cannot effectively stop a hit from a giant. Then a medium fighter could absorb a good amount of heavy hits, but the occasional fast strike will bypass his blocking. Finally heavy fighters could block and withstand tons of small strikes while blocking but average hits do reasonable damage still.

Third idea is for environmental weapons. I liked this concept in some of the games and hope they expand on it, such as having a temple fight but being able to utilize several different items (oriental fan, heavy oak chair, antique sword, blinding sand/dirt, kitchen knives, flag, etc. but all in one level).

Last one - unique movement styles. This is almost necessary in my mind; I've always hated how almost every character sidesteps in a close/exact same way. Reptile should actually walk and side-step/dodge his own way, with NOBODY doing it the same (he's closer to being totally unique than the more human characters though). I'd like to see each fighter move in totally unique ways, as in reality they would.