For me the warzone mode is one of my favorite games, however I think that you could add heads of the extended universe of Halo as they are tartarus and Ripa Mororame, although the latter could only be added if the unsc contacts the Spirit of fire , You know to justify their appearance with the records of the spirit of fire, or even add bosses who belong to a colony, what do you think?
Feel free to use one of the existing wishlist threads.