the plexiglass ring has been mentioned before and i think it's perfect. it gives better visibility than either the cage or the ring, it provides the security needed by clinchers, and it allows cameras to get any angle of the action.

that said, what about a six foot deep pit? You know having animals or people fight in pits was the oldest form of gambling. It's also the origin of the term "pitted against each other" and "pit boss". And then you could say you are a pit fighter instead of a cage fighter.