This might not be the best idea around this but I figured as SS will probably need to make the duels a "non-deathmatch" duel I was thinking when an enemy gets to 1HP instead of dying or falling over they get Stasised or frozen in place by a Force Field, the generators for these Stasis force fields would be those brown things protruding from the roof you see in the screenshot. This would make a lot of sense for a non-sentient being as when a Rancor, for example, takes too much of a beating they are forcibly frozen in place so it will stop fighting and won't get itself killed.
In this case, the enemy would be standing Neutral behind the Force Field then they are turned hostile when the Shield goes down and when taken to 1HP they go Neutral again and become Stasised until the round is over.
An idea for sentient gladiators would be Iridorians, the yellow space suit guy from the Manaan Cantina, you hear so much about how his species is so deadly and sadistic but you never actually get to fight any of them.