Are you thinking about a playlist, maybe a map (forge)?
Or do you just want something different, perhaps something to consider on the next halo game?
For Halo 5 or 6, I would like to see Flood take on it’s own mode.
Return infection as the living dead playlist and expand Flood into it’s own bonus mode.
6 v 6. Spartan vs Flood.
Spartan must complete an objective while the flood try to stop them. Oh and the flood won’t just be combat forms. You could have ranger forms, carrier forms, Stalker forms and Tank forms.
I would like to see Heavies for BTB and shieldless flood so that a single shot to their head drops them.
They need a gold gravity hammer in the next halo 
Community Test and Big Team Community Test rotating every two weeks with some Forge maps and new game type variants on the existing maps.