Considering that it was promised that we would somewhat soon get a coop update/DLC for infinite and seeing how MCC coop always had additional skulls for coop, I’d like to make a suggestion:
What is AI Director?
It’s a fancy name for environment, reactive to player status and actions that was implemented in Left 4 Dead (but I actually know it from another game - Alien Swarm), which primarily created additional and different threats to the player(s).
How does it work?
Well, according to L4D wiki:
… Director places enemies in varying positions and numbers based upon each player’s current situation, status, skill, and location, creating a new experience for each play-through. … Moreover, the Director is responsible for spawning additional health, ammo, weapons and special infected, like the Witch or the Tank.
In a sense, Infinite already has an equivalent to AI Director: when you grab a Wasp, all of a sudden, Banshees come out of nowhere and try to intercept you (most of the time). My good example would actually come from Alien Swarm: my friends and I decided to play it with AI director on after playing through a couple times. So the game apparently decided that we were strong enough, so it spawned a bunch of mid-game NPCs and sent them roaming directly to us to the very starting location. Imagine our surprise when after fooling around at newbie location that teaches you to duck to pass obstacles we got slaughtered by a bunch of midgame mobs coming out of nowhere 
Why would this be fun?
From my experience with MCC, nearly all Halos do “difficulty” by making enemies tougher (or making you weaker), which has its upsides, and a huge downside of turning difficult areas into a grind. This skull would allow increasing the difficulty not by increasing quality of opponents, but rather their quantity and unpredictability… Imagine if you’re going on a hog with 5 rocket marines (admit it, you already tried that) across the ring, and after analyzing the threat you emit, the game would spawn a couple phantoms tailing you and blasting you with everything they got, or placing 4 hunters directly on your path with a support from grunts with shock weapons. Or maybe a random ghost would spawn somewhere on a map, the sole purpose of which would be to get to you and run you over. Or if you’re sniping somewhere (next to a propaganda tower, maybe?) you would have 3 cloaked Ultras with swords spawn behind you… I would be against AI director taking over story instances, though, and would limit it to open world only, but that’s my opinion.
What is needed for that?
A bit of coding, I guess, a skull, perhaps, because that’s how these kinds of difficulty modifierswork in Halo, and certainly, absolutely, a pause function in coop. The downside of the AIDirector is that it always hunts. Even if you’re AFK in the safest spot possible.
EDIT: Ah, yeah, and you can call it “Offensive Bias” 