The thing that annoys me more than anything else about AAA guns is that they are only better than infantry when defending against an enormous stack of planes. If you spend 15 IPCs on 5 infantry, you get 5 HP and 10 defensive pips that roll in every round of combat. If you spend 15 IPCs on 3 AAA guns, you get 3 HP and 9 defensive pips that roll in only the first round of combat, but that have the potential to eliminate enemy planes before those planes can score hits against you. So the question is, how many hits would they have to score against you to even up that gap? At least 2 hits (since you can use your extra 2 infantry as ‘fodder’ and still come out ahead), and probably 3 hits unless your opponent is strafing (because the infantry’s ability to keep on rolling dice will let them pull ahead in ‘total’ defensive value as the battle goes on even if the advantage is to the AAA gun on the first round of combat).
So the break-even point for AAA guns is somewhere around an attack by 6 ftr OR 2 ftr, 3 bmbr. No matter how many AAA guns you pile into a territory, your opponent can still profitably attack you with ground forces supported by 3-4 planes. That’s really stupid.
If you have really dense flak coverage, a territory should become a death trap for planes, and even if you only have one AAA gun in a territory, it should be able to trade itself very profitably against attacking planes.
Mechanically, to make that happen, I would say get rid of the pre-emptive strike ability – it’s unnecessarily fussy and it’s too hard to predict. Instead, just give each AAA gun a single combat die that hits on rolls of 4 or less, but the die can only be applied to hit (and must be applied to hit) attacking enemy planes. That way the AAA gun packs a noticeably stronger defensive punch than infantry for the price (5 IPCs), but is weaker on HP and is useless for anything other than deterring aerial attacks.
Conveniently, this new AAA unit would cripple the ‘light trading’ tactic that currently serves as the lynch pin of orthodox strategy on the 1942.2 map. Planes really, really don’t want to trade lightly against territories with AAA guns.
Note that even though this makes AAA guns much stronger than they are now, they can still be overwhelmed with a large enough air force. Suppose Germany is attacking with 1 inf, 1 art, 5 ftr and Russia is defending with 3 inf, 1 AAA. Germany rolls an expected 3.1 hits, versus Russia’s expected 1.8 hits. Germany loses 1 inf and 1 ftr (-13 IPC). Russia will have to lose 2 inf, 1 AAA (-11 IPC) because if it loses 3 infantry then Germany could retreat the planes and mop up with the artillery unit, which can’t be hit by AAA guns because it’s not a plane. In the next round of combat, Germany attacks with 1 art, 4 ftr for a virtually guaranteed hit, and Russia attacks with 1 inf for 0.3 hits. Germany loses another one-third of a fighter (-3 IPC) and Russia loses another infantry (-3 IPC). Germany seizes the territory (+2 IPC), and so the TUV exchange for the battle is even (14 net IPCs lost for each side).