I know this is a game but AA shot down very little.  It reduced damage to the fields, I think a one hit reduction is far more important then you think adn reflects what the AA was used for: keep the bad guys air away from you dudes on the ground, bombers had to fly much higher and straffing by fighters was much more limited.  Maybe allow an AA one to sit on the field and one to sit on the dudes?  This is for US AA AFAIK, IJA AA was far worst, I don’t know if the USArmyAir lost any plains to ground base AA, and clearly not the 50 or so planes that each counter represents.

First let me say that I’m not too worried about AA ratings of ships, or if BB can sink subs etc, I just know these are fleets and the BB maybe one or more BB with 1 or probably many more DD etc.  What I do have a problem with is:

1. As far as I know, no costal guns of any sort (real costal guns or plain artillery) ever hit a ship during this champagne.  The would IMO only work if there was a direct landing against a beach something that neither side would do at this point of the war.  Yes yes Wake was a different story because there were no beaches that were NOT covered by Costal Defense (CD).
2. AA is way way way too affective, once again as far as I know, few, very few planes were shot down by AA.  AA made planes fly higher and thus reduced bombing accuracy and reduced strafing.  So in game terms the presence of AA should only reduce the hits that planes get on defending ground targets.  One defending AA would reduce one hit from the attacker.   I think I would limit the AA to one per target type, so one for each airbase, and one for all ground units.
3. Tanks were used by both sides, and as the USofA got use to tanks in the jungle, they became very effective and by mid 43 no offensive was ever considered without getting as much armor ashore ASAP.  I will include the half-track with French 75 mm as “tanks” at this stage of the war.  The IJA type 1 Chi_Ha tank with a short 57mm was actually a reasonable jungle tank.  There one employment was badly mistimed being mustered during a heavy barraged and then led across a sandpit into American 37 mm and half-track 75mm guns.  I have some ideas how to get a few units on both sides to reflect their capabilities as well as their huge drain on supply and maintenance.
4. Simplistic game and too bad it can’t or does not reflect some national aspects such as much better American AA, especially say game turn 4 when proximity fuses would come into play.  Or that only the IJN fighters can fly about the same distance as the Betty Bombers, the USArmyAir need to wait until turn 5 when the USArmyAir would get at least one P-38  P-47 a turn.