You could also create a Master AI controller. Like you have a squad of men. the talk to the Squad Commander(which is a separate object) This object controls the men in that squad's behavior, and through the commnuication, you change the settings of that commander, and all the men under him respond accordingly. But the functions of how to walk, run, shoot are all controled by the actual character object, but where to shoot, how to sneak up and plan an attack is controled by the Commander object(Which could also be one character or not a real game object at all).
By doing this you can create the sense of a really smart AI, but really its only one AI, just telling multiple entities how to respond.