Fighter jets. I know that many people did this suggestion so I just wanted to give my input and idea aswell.

Personally for me it would be the most important addition to the game since I love air combat. Since I understand that there can be many limitations on achieving that, here are my suggestions:

1. The aircraft itself could have 2 or 3 guns at least at the beginning. 1st would be cannon like apache has (30mm) so it could kill both air and ground targets. 2nd is homing IR missiles like talon and AA vehicle has for a2a combat. Third could be a simple dumb bomb, but as the any type of bomb has not been implemented yet, this is debatable.

2. Runway/take off. I really like how the Project Reality BF2 did the runway. They did not extend the map itself, they just put the runway far behind the spawn which would be HQ. Here you can land/repair/rearm. It is simple "block" like looking structure. If that would be hard, the spawn could be already in the air like BF1, BF6 has etc. Repair/rearm zones just expanded behind the HQ area (in order to start repairing, rearming, you need to fly in that zone, so basically staying behind HQ for a while)

3. Increase vertical fly range. Then it would properly seperate a2a combat. Littlebirds would fly as low as now in order to hit something. Now apache could hover way higher so it can stay out of the aa/talon zone and gunner could shoot. But then there would be fighter jets, which could hunt each other, apache, little bird etc, so it would divide the combat into layers. Also with increasing vertical fly zone you can decrease rendering distance as it is now so theorically there could be no performance impact. So all in all littlebirds would need to defend mostly from talon/aa vehicle, apache could fly high (although gunner would be shooting blindly (because of the rendering distance)) but there would be a danger of fighter jet. And if the air is cleared, fighter jet could CAS.

As a developer myself I understand that there could be more limitations, however, if you'd like please reach me I would really like to help to brainstorm this idea more.

Also for countering the argument about maps being too small, - it's enough. To be honest for realistic actions I think even BF3 maps were too small for jets, however, they still were there. There is no need to expand the map physically, just allow more freedom in the air (point 2 and 3) and in the air there is no details anyways