OK, I had this idea acouple of days ago, and I was trying to think if it could be put into OFP.
If someone made a bomber like the Pe-2 Rusian one with a non-playable tail gun, this might be able to work.
When you're flying (alone) in your bomber, the tail gun (it doesn't have to move) locks onto a enemy plane on its own. If that plane goes a certain angle away from the gun (say, 90 degrees right of it etc) then the gun targets a different plane.
When you (the pilot) fire, the gun at the back shoots whatever its targeting at the time.
There could be something to tell you if the gun has a target or not, such as a radio message saying 'Bandits on our six!' or 'Damn, i've lost him' etc.
Just an idea, would it be possible?