-Caution: Blast of Ideas-
Some good stuff, here. Although I rather like the hovering maneuverability of the Airspeeder, all in the name of balance, right? If we go that route I'd also knock down the armor a bit. Make it so that it barely survives a stormie-torpedo, and that a few follow-up blaster shots will cause the health to degrade terminally. That way, if the airspeeder tries to go for a hovering attack, all it takes is a torpedo and a few hits with a handheld blaster to send the craft to its doom.
Also, the tailgunner position is fairly pointless right now. In fact, in the few times it is used effectively, it makes an already-hard to hit craft even more hazardous for TIE fighters to attack. It gives the craft a passenger position, which is effective, but I'd try and give a little more of a point to it; say, you give the blasts a larger area of effect in exchange for lowering the rate of fire (also, increase the weapon's power against AT-AT's, so that airspeeders can go for the kill by circling around the walker's legs so that the gunner can land shots on it {again, hovering in place to accomplish the same end makes it vulnerable to small arms fire}). With lowered hovering maneuverability, it would make it harder to use cleanly as a hovership-harbinger-of-death, but when the airspeeder completes a strafing pass, the rear gun can add a few insult-to-injury shots to the strafing run, perhaps taking out a stormtrooper or two.
Remember, the tow cable was designed to haul cargo crates, not to topple Imperial assault walkers. Rebel modifications gave the airspeeder it's twin blaster cannons (and presumably the rear laser) and enough armor to withstand small-arms fire. While fast, this craft was not originally designed to be a war machine. Even a TIE fighter shot or two should wipe it out. And heavier blasters shouldn't be that much weaker. Using an airspeeder to strafe ground targets shouldn't be the superior alternative to the same in a TIE Fighter or Y-wing (I know that the bombs are being fixed).
Also, perhaps instead of reducing the numbers of airspeeders on Ryloth outright, have two of the speeders be as is and the other two in their factory states (unarmed and more maneuverable when hovering, except maybe keep the rear gun) on the 16-p and 32-p maps. This gives the Rebels a decent aerial transport package to counter the Imperial Lambda shuttle.
One last thing about Ryloth in general. The Imperial Star Destroyer in orbit just delivered a withering laser bombardment on the surface. Any Rebel that wasn't suicidal would retreat to the safety of the base and the underground mines. I'd make the first two (or four, in the case of the 64-p map) control points neutral at the outset, with only the Rebel Base and Mines control points in the hands of the Rebels. The Imperials still have to capture two points in order to make a move on the mines, but the Rebels no longer start from a position of tremendous strategic advantage (enemy bottled at one point, superior air power, superior anti-air power, and time working to their advantage).
GC Veteran (0.14-R6) "General Jafar"

