Expand the Halo universe is not a bad thing, of course with moderation because we do not want Halo baby toys. A good idea would be a Halo mobile game. We know that playing in a “small magic box” (cellphone) is not a big deal, but a simple Halo game could work. My idea is to make an RTS, similar to Clash Royale, because Halo Wars 2 Blitz mode uses a card deployment sistem, but not too similar, because instead of having defensive towers you would have only a firebase with some turrets, and the map would be signifficantly bigger to have vehicles like scorpions. This ideas may vary but the concept would be the same (not plagarism). The art style would be the Halo Wars 2 one and it wouldnt be a cannon or affecting lore game, just a game to be played.
And I know that Halo Spartan Assault and Strike are abailable, but im speaking of a different concept
That would be pretty cool if done right. I doubt it will ever happen though.