Give me some "holy sh... did that just happen" ideas

[Feuerfalke]

On ground:
Spawning: It would be great if you could e.g. choose the position where you spawn either from fixed options or freely in a given area. This would also add a lot to squadron activities and limit the occasions where teammates have to taxi 10 minutes to coordinate a teamstart.

Airfield Activities: Another good point already mentioned is airfield activities. I wouldn't even go as far as interaction with ground-crews, but e.g. fueltrucks or vehicles being spawned randomly around the airfield when the mission starts. That would also make raids on airfields a lot more interesting.

TASKS: More decent briefing. E.g. by assigning different tasks. Simple example: Teamgame, each with groundtargets available: Choose between Task Strike, Escort, CAP or FreeHunting. You could even have specific briefings and loadouts per task. If this would also be listed e.g. in score-screen, it would be much easier to coordinate even without sophisticated c3.

Tower communications would also be nice, e.g. informing about wind- and general weather conditions and takeoff-direction.

In flight:
C3: Ground c3 by not only reporting enemy planes located by spotters or radar, but also from groundunits unter attack and leading flights to corresponding areas. Even if not realistic, it could work like this:
Unit A is under attack, c3 calls out location and asks who will assist (not all players fly in teams or squadrons, so IMHO you have to account for this at least online) - Then pilots have the choice to either accept the mission or continue with what they are doing.
As with the example with Tasks above, you could also integrate this and change tasks inflight.

More communication especially with gunners on multicrewed bombers, giving position, number and types of attacking aircraft.

Playable ATC/c3

Ingame communications only with Push-To-Transmit. Really, really, needed. I don't want to hear pilots barking at their wifes or sneezing or eating. It does more than killing immersion...

And of course my all-time-favourites:
Killmarkers and individual markings

Well, just a few ideas