I propose that players are able to use the arenas without fear of some one uninvited joining the fight.
Just because in the past, in the original PVP arena, anyone could join at anytime, there seems to be a belief out there by some players that they have a god given right to do so just because we allow pvp and this false assumption is at the root of the question posed by SharpSerac.
If you go to a dedicated pvp server you get sent as a group to an arena for a fight and while you fight no one else can join. In the same way as you do egg wars or bed wars or any other similar game.
This could be done by those in the lobby for an arena being transported as a group when the sign is clicked and no further tps in until the arena is empty, or the existing players click on an accept.
It is extremely tiresome for those of us that are noobs, that we cant have a fight with out some full netherite person loaded with totems butting in. It would mean you could go to an arena and say have a punch only fight, or a iron only gear fight. Whatever rules you choose.
I also propose that we have a PVP ladder, this would also require that it is possible to have an unintertupted fight.