Price won't help (one-shot asset just sucks), it just need rebalance.
I personally love the idea of having only 20-rated sum of LBXes on ASF.
Another way is to create air-LBX-es. They may got way lower modifiers against ASF. So, it would require at least 2 salvos to kill Sulla. Or devs can make bigger Air-LBX loaded with slugs, not pellets (typo different ammo). Make slugs travel time lower, damage higher then AC20s. They would still be effective against ground, but hard to use against air.
Oh, the idea looks good. Special Air-LBX 10 and Air-LBX 20 loaded with slugs. Damage per shot like 1200 for Air-LBX 20, 6 seconds reload time. Travel time like 2-3 times faster than AC20, range 450 meters. May be - lowered precision (like shotgun slugs) so ASF have to get closer) They would be very effective against ground (same as now), but very hard to use against air.