For CoH, I created an enemy group that was designed for flight. I always hated AE didn't allow for enemy placement. I wanted my villains on the rooftops through the zone...even though CoH didn't allow for flying combat....I still wanted the battles to happen on the rooftops.
So that would be my suggestion.
(Admit it, when you were on those huge buildings you wished there was somebody up there to fight, didn't you?)