Currently lategame is almost completely decided by the person who has more Air dominance. Land armies are just too slow and are either shredded by air or take so long to travel that it is easy to build a counter in time. That Air power is decided by solely spamming one unit: the ASF. I don't think this is particularly interesting for gameplay.
It is virtually impossible to shield armies from air attack in a cost effective manner. Mobile AA is just too weak at actually fighting both gunships and especially strat bombers/ASF. The current implementation of Mobile T3 AA is basically a compromise between people that did not want to see any units added to the game and those that saw the need for a unit to break the complete dominance of air in the late game. This compromise consisted of introducing the unit but making it shit so nobody actually uses it. I think this is a mistake. Buff the effectiveness of T3 mobile AA so it becomes an actual threat to T3 air units instead of a waste of resources and thus make air balance ever so slightly less about just spamming ASF after ASF.