Honestly, IL, I don’t think cruisers would be the correct unit.
In World War II, America and Japan were actively researching Anti-Aircraft defenses (and Anti-Submarine defenses) for their Aircraft Carriers, not their cruisers.
If you consider a carrier representing a carrier group, this becomes even more logical a choice for AA Guns.
Here’s how I see it going down:
Aircraft Carriers can be outfitted with technology to have AA Guns that fire just like ground based AA Guns. Only one per sea zone may fire, but it may fire at each attacking enemy aircraft.
Basically, the AARe rule, but instead of Battleships it’s on carriers.
I’d also like to see a technology to increase Battleship effectiveness to 5 on attack (like Super Submarines increase submarines to 3 on attack.)