One thing that Halo AI does pretty ridiculously is having marines rush forward and die when the player is hanging back and dropping enemies who don't react to their comrades getting sniped. There's really no fire & maneuver.

So for a mod like this, would it even be possible to group allies and enemies together, sorta like in Ubisoft's "Brothers in Arms" series? I'm not a modder myself, but I imagine it could be something as simple as "Characters 1/2/3/4 do not move more than X distance apart unless using evasion, and try to rejoin if separated."

Reach did have a fire teams mechanic, so perhaps that could be leveraged, too...?