The OP provides a wonderful idea for gameplay, but presented as a response to the wrong issue. The ENY system, when properly implemented, is meant to limit the ability of the strong side to attack the weaker ones, thus equalizing gameplay. A destroy-targets-to-limit-the-enemy system encourages hordes and massive side switches in order to garner the numbers to carpet bomb a now-indefensible country into Hurricane Mk. I oblivion.
ENY does not limit the strong side's ability to attack the weaker side(s), it simply forces them to take what is less "easy" for them to get the job done.
Instead of P51D's fully loaded with ords, the F4U-D, F6F, etc are tapped. Not a real big disadvantage, really. It isnt until those heavy hauling fighters are grounded that the attackers are limited in fighter/bomber choices. Not until the ENY gets to 25 or so. Once all the 2000 lb+ ord carrying able planes are grounded and the 109's, 190's, (all) Japanese fighters are forced in to the jabo mode is the attacker "limited", at least in the jabo mode.
Regarding bombers... losing the B29, Mossi B 16, and Ar234 is hardly a worry. It isnt until the ENY gets to 20 that the lancs, B17, b24, etc are grounded.
The ENY system needs a tweak, no doubt. But HTC holds the password and the "coad".