one of the most important missions aircraft take part in is destruction of enemy air defenses, however currently the only air defenses are those around airfields, and the spaa escorting convoys.
I suggest the addition of surface to air missile sites, placed behind airfields, such that their effective range covers much of the territory from the airfields and backwards.
doing this would make allied territory seem safer than it normally does, as it would prevent aircraft from simply sitting behind enemy territory and waiting for people to take off, allowing for more head on encounters, which are more enjoyable for both players.
additionally this allows for missions to have objectives centered around destroying these defenses, making it easier for ground attackers to destroy bombing targets and airfields after their protection is removed.
such air defenses can include vehicles that would normally not be placed in the tech tree; such as the 2k12 kub system for the soviets, or the mim-32 hawk for american teams.
additional radar sites could be used to reveal enemy aircraft in allied territory, incentivizing players to destroy these sites to give their team an advantage in combat.
this could potentially improve the player experience for ground attackers, who would now feel more useful to the team.
this could also improve the experience of the fighters, who can now retreat to friendly territory as needed. having a safe space to retreat makes it more like that players will disengage from fights, allowing for long range air to air missiles to have greater use, as players will likely want to engage enemies with missiles rather than risk chasing them into hostile SAM coverage.