I guess I can kick-start this conversation. I think we should replace Combat I for air units with something like Air Combat I, II, III just so we can keep the tree seperated and organized.
One thing I liked to do was call the promotions "titles" instead of a I, II or III
i.e.
Veteran --> Top Gun --> Ace (same as the current promotion), but either way it doesnt matter.
I personally dont like the "Air-to-Air" missiles family concept of promotions. I always thought they should just be 1 promotion. (see note on the bottom)
Veteran/Top Gun/Ace : +X to base strength (ace also increases evasion)
(could also call it Ace I, II and III)
Interception I, II, III : +X to base interception rate
Range, I, II, III : +X to opperational range
Bombard (rename?): +25% vs Land Units
Torpedos: +X vs Water Units (also available to submarine/naval units)
Gatling Guns: +X vs Air Units (also available to helicopter units)
Air-to-Air Missiles: +X vs Helicopter (also available to helicopter units)
Ambush: +25% vs Armored (standard promotion)
Chaff: + 25% vs Missile Units (define cruise missile as a "missile class")(also increases evasion)
Radar: +X Interception rate (for land/sea based units)
Maybe a few other specialized promotions for various areas.
I think this limits confusion (both for AI and Human players). I am not sure how the AI would react to the +5 vs A, -5 vs B. I personally have never tried such promotions, nor am familiar with the logistics of the AI. but would they actually judge the negative number when making the decision to use the promotion? If it just picks the promotions randomly, then giving it a negative value can easily be countered by a human player.