My thought about this is that fighting over something meaningful is often much more intense than just fighting for the sake of fighting. Removing the chance that the hangars can be destroyed may itself effectively destroy the fight.
I this idea would help with that. It's sort of a compromise on both sides, but still benefits everyone.
1 hangar dead, no 0-5 ENY planes, 2 hangars dead 0-15 ENY, 3 hangars 0-25 all hangars only 35-40 ENY planes can take off from a base. That way you can't disable players from taking off (which promotes combat), however for the defenders failure to keep their hangars alive, they can only fly 35-40 ENY planes. However, it doesn't give a complete edge to the attackers, because the defenders can still take off in planes. While they might be 'lower quality' or harder to fly, they can still get kills in them.
DO you guys think this would work? I personally think there is nothing wrong with it, I think it gives a compromise on both sides. For attackers, they give up the ability to fully disable a base, however get planes to vulch (and fight). Defenders give up their lower eny planes if they fail to effectively defend, however, if they lose all 4 hangars, they can still defend even if it is with planes they may not prefer to use.