Why do we even need mobs? Wouldn’t it just be easier to have a large,multicrew teamfight? No new plugins, no special gamerules, just pvp combat an heaps of fun. 😉 (perhaps this is simmilar to the ship battles Max does, just with a slightly different objective and a different feeling.)
We could also use ships and forts with cannons ect. for combat, just like Spectre_Orleans suggested. But an arena should surfice as well.
This “idea” could also be implemented as an event of some sorts if need be. Handing out rewards for example based on the number of player kills collected.
To make this sugestion appear fair to everyone, I would not close my mind to the idea of keeping the playercount and gear on each team equal. Though executing this battle with every participant in god gear might be too expensive for some players, so maybe iron gear should be used? Idk. We shall see.