The ability for CAS to destroy player tanks isn’t a problem per se - it being the only thing CAS has to do while being relevant IS. CAS has no “healthy” way to contribute to the gameplay loop currently. In addition to sleazy revenge mechanics, unavailable/inadequate counters (of which your idea of SPAAG stealth belts I FULLY agree with), and a total lack of the majority of real objectives for both CAS and tanks to accomplish.
CAS and Tanks are currently thrown into a barrel-sized pressure cooker with nothing to kill but each other. Of course it’s gonna suck - neither is built primarily to take out the other save for some oddball specialized planes like the Duck.
I do see at least some potential for drastic changes taking place, because we have the foundational mechanics to expand upon in the game already.
For example, high tier tanks all get drones and strike drones - how hard would it be to expand on that idea and take a page from Naval so all players regardless of their aviation preferences get both fighters and CAS with preset loadouts in their lineups by default that are free to repair? Then every user has aircraft of their own to counter enemy aircraft, guaranteed.
Spoiler
If they then still choose to complain about CAS, it’s now their fault, not the game’s. “Tank-Only Players” would effectively cease to exist, which is a net benefit for a game that markets itself on its combined arms aspects. If the game gives you all possible tools and you choose not to use some of them, you have nobody to blame but yourself if you get blasted by something best-countered by one of the tools you haven’t learned to use.
Giving SPAAGs that lack radars a short-range lead indicator can straight-up copy the one from arcade but make the range it shows up half or less.
Removing the kill camera from live matches and forcing all planes to runway spawn are also piss-easy to do and would go an immense way to truly solving the otherwise endless CAS debate.
The concept of tying spawn zones to caps has existed in the game for years, both in the old [Break] mode and also Naval EC. This would free tanks from the fishbowl maps that make finding tanks as CAS so easy, greatly cut down on spawn camping, and just give tanks more room to move.
The artillery support tanks call upon were once a map target outside the tank map for planes to go kill, why not bring this back but make the artillery use player tank models like the M44, M55, or various high tier SPHs? Gives planes something else that is actually relevant to match outcome to go kill that can’t go jump on the forums and whine endlessly.
The problem is the ability to whine in and of itself, it obscures the mechanical flaws with how CAS works in a big cloud of aerosolized piss from people screeching “CAS OP!!” at the top of their lungs.