I'm setting up something similar - I have a randomized group spawn at the beginning of the mission (random flag value that triggers each group).
Let's say one is a russian plane that won't shoot at the player, and the other one is a north korean plane that will attack.
I set the russian group to weapons hold and let them de-acticate their radar via advannced waypoints.
The North Korean group is set to weapons free, but via advanced waypoint menu, you can let them use their radar only for the attack - at least with a group of MiG-21s, this worked quite well.
For fighters with better long range capability, I guess the way described by feefifofum might be even better. I'm gonna test that one. Especially because you could also tell the bogey to turn around as soon as it has been intercepted.