Here's how I would want it to work:
Same controls as usual.
Autoblock.

The catch is that to autoblock successfully, you have to be in a like stance.
Likewise, to attack successfully, you have to be in a different stance.

There'd probably be powerups and stuff, but that's the gist of it. (It'd be even better to introduce different characters with their own abilities.)

Someone like Henry might have similar A attacks as Travis, but different charge attacks and B attacks. Someone like Destroy Man would be completely different.

The main point of this is to explain the blocking function. Evasive techniques would remain the same (slide and darkslide), but blocking couldn't be done with a button--it would far deter from the already somewhat limited combat elements.

But that's just my thinking.

I can kinda see that. It's like Multiplayer on Starwars The Force, right? Except you replace the Force push stances with Defense and Offense stances.