So nowadays, the only strat that most alliances come up with when they fight wars involve pummeling air. It can be awesome when you're winning, but it isn't as fun if you end up on the receiving end of a blitz. Yes, there's the possibility of getting ground control, but really doesn't do much if you already lost a majority of planes. You'd still be stuck demilitarizing or doing "hit and decomm" if you didn't want to get your tanks airstriked by enemy planes. If spamming planes is the only good strategy in alliance wars, then politics and war wouldn't be much of a strategy game.
To counter this, I propose that we replace the current ground control mechanic with a level system. This level system is somewhat like how you used to have to get 6 ground control victories to beige, but instead of the levels being progress toward victory, the levels would represent how much airfields have been captured. I propose six levels with each level corresponding to the percentage of the "airfields" of your opponent that you control (i.e if you are at level 2 control, this would mean you control 33% of your opponent's airfields, which means your opponent can only use 67% of their airforce). The levels of ground control would be 17%, 33%, 50%, 67%, 83%, and 100%. At the last level of ground control, your opponent can't use airforces against you at all. This would also mean that if your opponent has air superiority, then they lose it. Each immense triumph ground victory would result in an increase in one level of ground control, and if your opponent gets a pyrrhic victory, a moderate success, or an immense triumph while they are under ground control, then you lose one, two, and three levels of ground control respectively. If someone else gets an immense triumph over you, then you would also lose a level of ground control over all your other opponents.
Those are the basic mechanics. I also propose additional mechanics that may or may not come with this proposed change:
1. Modify the blitzkrieg policy so that instead of allowing you to deal extra damage (for a limited time), it will instead allow you to gain two levels of ground control instead of one on the first attack you make during a war. The downside would be that during the first attack, tanks will have an additive combat value modifier of -20%. (All you need to do to counter blitzkrieg is to have massive amounts of tanks, just ask the Russians during the Battle of Kursk)
2. In the event you make an attack where after the attack, your opponent no longer has any ground forces (soldiers and tanks), whether this is due to you wiping out their ground force, or them not having ground forces in the first place, then an immense triumph will add three levels of ground control instead of one.
I acknowledge that this new mechanic may make ground forces too OP, as airforces are right now, so there could also be a similar system with air superiority.