perhaps the ai could be like in bf3 where the guy comes on the radio and just tells you something every three minutes or so and places an objective marker on it and perhaps it can tell you when an enemy gets into a power vehicle (gauss hog, scorpion, banshee, mantis). I would not mind the return of fireteams from reach, it was tactically challanging because you could either leave them to their own weapons and let them all die, or give them enemy weapons (needler, plasma repeater, fuel rod cannon) and let them help you in the mission often surviving until the end.