Doesn’t change anything.
The correct solution is to prohibit weapons of AA systems for the first 10 seconds after spawning (spawn protection lasts 20). This would be fair to SPAA, allowing them the same amount of time to recognize and have a mental picture of the airspace, as well as allowing aircraft to react to radar pings or visual acquisition in time, as would be in real life. This restriction is really only needed at about 9.0 and up.
This solution is justified not only by its positive effects on balance, but also the boost to realism. In real life, SPAA vehicles don’t just pop into existence. Even with radar off, SPAAs can still be detected visually. So it’s unfair to let them spawn and immediately start deleting aircraft while being invincible themselves for an extended period of time.