@SAS:
Or what if each airbase is required to target a different territory with its paratroopers? That would limit the shield effect to two max for each territory, which still makes any IPCs spent on building extra airbases worthwhile (rather than only allowing two of them to be used each turn), but still putting aircraft at risk more than flooding a single territory with paratroopers as flak magnets. That way a defender can load up on AA and it still be worth it because the paratroopers have to be spread out.
Let’s do the math. Using my suggestion of 2 paras per turn per theatre. Let’s say the USA has the tech and he he is playing to use them as shields. The axis player is super lucky at rolling ones:
The USA sends 2 paras as shields against Germany and 2 against Japan. They are big battles with lots of air support. The axis both get 2 AA hits. We’ll even assume the USA was only using fighters, the cheapest aircraft. The 4 paras just saved the USA 28 ipcs (7 ipc cost diff times 4). on top of that he gets to move 4 inf for free each turn saving 14 ipcs in transport costs. This is already a HUGE benefit. I would still consider this a very powerful tech. Your suggestion helps with the AA thing a bit. But think about this. Aside from the huge cash benefits I have already shown, each airbase reduces your need for 1 transport ship, so the power has huge incentive to build more as they are basicly unsinkable transports. The 15 cost is nothing if it gives you the normal airbase benefits plus the ability to move inf without ships.
Again, even at just 2 per theatre per turn, the USA is potentially saving 28-36 (if bomber shields) ipcs per turn, plus they are much more fluid with their inf, which can drop from different airbases each turn. It’s a big tech to score.