I would really like to See Flood fighting Promethean A.I’s to give us a glimpse of why the Forerunners had to use the last Resort Halo Rings to wipe the Galaxy clean! I think it would be awesome if Chief had a mission where he had to run in the middle of a conflict where the Flood would be having a full blow out battle with the Prometheans! Kind of like how we seen the covy fight each other in Halo 2!
I hope we see promethean knights vs flood in the campaign, that would be awesome. Flood vs Prometheans VS Us, it would be awesome and would bring back some memories from older games. One thing that really disappointed me in Halo 4 was when the storm faction and the prometheans became allies, hopefully they make up for that and bring back the flood.
Idea for firefight. Make a match type where two enemy factions are fighting (Flood vs Prometheans) and your fire team is stuck in the middle and has to escape to a LZ or until evac.