It would be cool if they had invasion but with a larger player cap and four different teams: Human/Covenant/Promethean/Flood. Which teams are playable could be map specific. Human Team would have Spartans be playable and they would have ODSTs and Marines as allies. Covenant Team would have Elites and Brutes be playable and they would have Grunts, Jackals, and maybe Hunters as allies. Promethean Team would have Knights be playable and they would have Watchers and Crawlers and Knight Battlewagons, Lancers, and Comanders as allies. Flood Team would have Spartan, Elite, and Brute Combat Forms be playable and would have infection, carrier, and pure forms to serve as allies. They should at least have this in Halo 5 or 6.