K.O's could be done if, when the opponent is below a certain fatigue, the player does their "Signature Move" or one of their "Power Moves" which have low negatives if they fail but can only be used once.
I don't really know what a submission is though so... yeah.
I would think that "Favor" should be a stat of some importance. It basically represents the audiences "Favor" for the fighters. Maybe a high favor could result in some fatigue being gained back?
I was thinking something similar with the Finisher-Based K.O., the only issue being if they miss in the way you're saying, then they can't use it again. This is why I also have pondered the use of "Environmental Finishers" from Def Jam, as slamming someone's head into a concrete wall or an amplifier should be enough to knock them out cold.
Submissions refer to holds on a certain section of the body, such as an arm, leg, or neck, that cause pain and massive discomfort to whomever they are applied. The fighter under the submission must either get out of it, or forfeit the match. This is the system used in real life sport wrestling.
There will be a Reputation factor for the relationship with a fighter to their audience, though I don't see how it would result in them getting healed. I'm not a big fan of healing in the first place, I think the best matches are when the last beaten fighters struggle at each other in a scenario where one hit could end everything.
Real Life. Use formulas from physics to calculate things.
It is quite literally the perfect system.
I feel like that would detract from the game's Def Jam and WWE Wrestling, where the most impractical and inefficient moves were also the most spectacular and devastating.