Well, the Russians will likely have few artillery and tanks, so if Germany attacked the Russian stack with all its air (5 Fighters, 5 Tac Bombers, 2 Str Bombers) they could kill all the armor in the first round, greatly diminishing the Russian’s defensive capability (or if the Russians were on offence, the German air could kill its armor AND artillery, effectively neutering the attack and dooming Russia).
With the US- Japan starts with 11 Fighters, 8 Tac Bombers, and 2 Str Bombers, a much bigger Navy than the US with its measly 5 Fighters, 1 Tac Bomber, and 1 Str Bomber. And that’s if the US doesn’t send any aircraft to London. Just in aircraft alone, the US would need 149 IPCs to achieve parity- or the first 3 full purchases (if Japan did a J3). No cheap DD/SS fodder- no new carriers (Japan has 3 to the US’s 1). Japan will always have air superiority and thus always target high value ships (BBs/CVs) first.
I’m not sure where you get that the Allies have the advantage in Global 1940- all the bids are to the Allies (go look at the games being PBF), and many times the bid isn’t even enough.
If you wanted to use the air supremacy rules, it could be good, but you’d have to change the entire setup to reflect the power aircraft now have.
The obvious Allied counter would be to prioritize aircraft production, like in the real war (see: Battle of Britain, Battle of Midway, Battle of Kursk), which isn’t as daunting as your projections would indicate.
Because planes can’t land in newly-conquered territories, each side could use their air units to cherry-pick the other fellow’s best offensive units on their respective turns, resulting in a mutual neutering until somebody finally broke through.
It would be a bloodbath in the sky for the first few rounds, but the Allies have the economic clout to pull off air superiority in the long run… and with this targeting prize, air superiority would really mean something worth fighting for, for a change.