That sounds like a neat idea 
No reason why there can’t be, I’d be happy to make an underground arena or something for this if they actually go through with it.
That is true, although I think it’d be nice to have an automated arena where anyone can join at any time would be something nice as well. Players can still do more fun and custom things and their own events, but if someone is looking for casual pvp, an arena could be a cool alternative.
As is mentioned in the post, mcmmo can and would be disabled in the claim for the arena, just to even things out
Doesn’t need to be consistently active, it’s more of a side thing where you could ask someone if they want to fight in the arena, rather than having them teleport to you in some random place and fight there. I could even imagine people being able to duel players in the arena and set bets on fights, winner takes all.