In Halo 2 and maybe in H3 there was a way to limit the number of players on the map at a time, and my friends and I called it 1v1v1 (Uncreative I know).
We would limit the players on the map to 2 and play it with like 3+ people, sometimes even around 10 people, so the game would start and 2 people would spawn in and the remainder of the players would be spectating. Then when one of them died, one of the players spectating would spawn in and play the person who won the first gun fight, and we would play it with 15 kills to win.
It was a lot of fun to do especially at the tail end of a long night of Halo and I haven’t seen any kind of option in the custom game menu to do this on H5. I’ve also been trying to think of ways to effectively do it through forge since it doesn’t appear to be a game setting option, so if anyone knows of a way to do it or has some ideas of how to do it in forge, please lemme know 