again Nish isn't suggesting a free loading arena.
Nish: FFA can be easily re-created in a custom room. The Few training map includes multiple air spawn heights within a bowl that would be roughly the same concept. You would even have more control over plane choices by having the host remove those fast / cannon fodder planes that guys used to spawn in and do a couple of gun pass picks and then run. The max of 16 players would be enough for an on-going scrap.
Other than that you can easily amend the KOTH terrain with as many air spawns as you like. It isn't difficult to do.
Once you have the map and learn the arena settings you can have full control over planes, icons and griefers. Leave your PC running 24/7.

Wish granted!