Since the AA is a hot button topic atm, let me make sure Rocoteh knowa where I stand on that. It is only the AA batteries, not AA from units, etc. that is the problem. Even in vast quantities like major naval groups, unit based flak produces acceptable loss levels. If Riley555 spies on London, you will see they start with the AA battery in place. I wish there was some way to edit the improvement, but I don't think that is possible? There was an earlier version that required the airport to be built before you could build it, that might be one way to go. I still think removal is the best option at this point. Especially since my last report the Japanese did about 15 more sorties and the batteries shot down at least 12 of them.

The Japanese are completely stalled, and I am considering counterattacks...and it is still 1939.
Sorry to beat on the dead horse Rocoteh, I just wanted to make sure you knew I think the unit AA is just fine the way it is.
I've been thinking about artillery too. In that, like armies, a few in the hands of a player are far more potent then they should be. Have you ever considered eliminating pure artillery units altogether? Leaving defensive and naval bombard on units, maybe even adding a bit of defensive bombard to regular ground units if you still want to represent artillery that way. I mean how many great big independant artillery groups were actually running around? I know something like this would completely change the flow of the game, but I think it might be interesting! Taking cites would be far more costly for sure, attrition in your ground units would be heavy.
As far as lethal land bombard goes, after a lot of experience with bombing I am not sure if it is too powerful or not. Taking out units in the open is certainly pretty easy, but killing units in cities is awfully hard; you can hit improvements or flat out miss a lot too. There are plenty of countermeasures to air power, fighters and flak can really tear them up. You might think losing a few every turn isn't much, but your bomber force will be attritioned to death before you know it that way.
Speaking of bombers, I really think the basic bomber needs to have its ROF raised by one. As they are now,they are truly pitiful units. One more ROF is not going to turn them into the terror of the skies, but at least they would be marginally useful.