Thank you for the suggestion,
This is my opinion on it.
20x20 square would be really annoying, probably Pe android players will not play it.
Hive is not a practice server, what you are suggesting is for a practice server, don’t get me wrong but a sumo FFA wouldn’t really be liked on Hive in my opinion because Hive is more of minigames/gamemodes (like skywars/ parkour/buiding etc.)
This is all, have a nice day 