In a duel server, there are two players, and maybe N>=2 spectators. Maybe the duel server can have an option to run multiple duel matches simultaneously, so that the spectators don't have to switch servers to play?
It's just a thought. There are clearly some issues to be thought about, such as server load, and whether to synchronize match ending times to facilitate a pairing shuffle, or to let all the duels end independently. A quick and dirty solution would be to Ctrl+C Ctrl+V a map so that the map contains two copies of itself, and then controlling the player spawns by putting the four players in four different teams, two in each copy of the map.
It's just a thought. There are clearly some issues to be thought about, such as server load, and whether to synchronize match ending times to facilitate a pairing shuffle, or to let all the duels end independently. A quick and dirty solution would be to Ctrl+C Ctrl+V a map so that the map contains two copies of itself, and then controlling the player spawns by putting the four players in four different teams, two in each copy of the map.