I think things went bad with AT2. It became less AeroTech than AccountingTech for me. Arithmetic isn't an issue, but keeping track of a couple squadrons on a blank map, while the other player(s) do the same... It got old. I liked the squadron rules, but it was still boring by comparison to BattleTech. I think an Alpha Strike version of AT, AeroStrike, perhaps, might work. Forget the thrust versus speed, maybe by eliminating battles outside of atmosphere, and get it to move faster. I want to like the high altitude map and such, but in the end it just muddies things up when trying to have ground and aerospace units in the same battle.
I'd make ground attacks abstract, give fighters a single pool of armor rather than locations, have their Thrust and Overthrust become like 'Mech MPs, forget tracking fuel, and make their weaponry a single dice roll (and another single roll for location against a 'Mech) rather than rolling for each weapon like for 'Mechs (yes, it'd be devastating applying all damage to one 'Mech location, but fighters are supposed to overwhelm 'Mechs in that manner, so I think it'd work; it'd also make fighters fearsome against ground targets). Make their design rules closer to vehicles than to 'Mechs (right now it's sort of an amalgam).