The other night our squad was running a combat challenge when one of us was shot down. While in the tower, that player was able to see players within the radar, and they started performing the role of a combat controller (CCT).
It was actually very immersive, having someone direct roughly where to look and what directives to take, but not being able to see it yourself and having to trust the direction of a squad-mate.
I'd like to see aircraft with radar implemented, but - only the pilot of the aircraft can see that radar and the contacts that it picks up. I think this would add an entirely new tactical dimension to the game, where someone in a radar-equipped aircraft could call out targets to others, but other players would not be able to see the radar themselves.
The radar aircraft themselves would be relatively vulnerable and would rely on protection and cover from other aircraft. They would essentially become targets of strategic value. It would also open the game up for a new role to squadrons and to the MA - CCT's.
An example of such a fighter in WWII:
