Re: Assassin's Creed 2
No map, no hud, maybe eagle vision - haven't decided yet.
You both collect intel, and can sword fight each other (they'd have to fix the counters, to give you a chance to counter a counter and so on, or just do knock downs until they were on their last hit, then just reinitialize and have to collect more intel.
And you HAVE to collect a LOT of intel and save citizens and whatnot, don't make it a fast/easy task.
It wouldn't be bad, but I would NOT want it to be a focus.