Here are just some balance ideas I had that I think are too small to each warrant their own thread.
Remove ACU repair:
ACU repair right now is never utilized. Seriously, I don't think I've ever seen someone purposefully repair their ACU. More often it's a nuisance when your engineers assisting the ACU start repairing, forcing you into a power stall. If ACU repair could be taken off assist and required the repair order that would also work, but I'm not sure whether that's an option code wise.
Give Sera T2 PD power drain:
Sera T2 point defense is widely considered to be the best, as it excels against both single and multiple targets. Giving it some power drain like the UEF T3 PD would give it some additional disadvantages to balance this out, and would increase faction diversity. For that matter increase T3 PD power drain to something noticeable. A single T1 pgen is enough to sustain 4-5 of these bastards.
Make aircraft carriers require an HQ:
Making aircraft carriers is the only way to completely tech skip in the game, as you can go from T3 navy straight to T3 air. If they were to function as support factories and require a T3 HQ, it would make it more in line with the other production types. They could potentially still produce T2 air without an HQ, but the instant T3 is a bit insane in my opinion. Czar and Atlantis would be exempt.
Increase stationary T1 AA projectile speed:
If an opponent hits T3 air before you're at T3, there's very little you can do about bombers aside from T1 AA spam. Problem is even those are incredibly bad at hitting them. A small projectile speed buff would allow at least some measure of response instead of an instant GG.
Make Sparkies not follow enemy units when on patrol or attack move:
Sparkies are great, except for one extremely annoying habit. If you put them on attack move or patrol to reclaim, they'll then stop doing so to chase after any enemy unit that comes into their range. Basically do what you did for gunship AA to Sparkies.