In WarBirds there was no DarBar, but rather a colored arrow that pointed in the direction of the nearest enemy, or friendly. You then made note of the compass heading and flew in that direction until you either made contact, or another set of arrows came up pointing in a different direction. I mention this as a potential compromise to losing total DarBar as a result of losing HQ. Perhaps this method, or some similar facsimile, could represent the Coast Watchers, or ground personnel that were used to track aircraft in WWII when radar was not available. Bases would still flash but only at half the distance as they normally do if HQ was fully up, but if HQ is taken down fully, only the arrow (Coast Watching) system would be available until HQ is fully restored. Now this arrow would not appear on the Map, only in your cockpit, so you might have to communicate with your Team before taking off to be able to make full use of this secondary system; if you were already airborne, the system would take effect immediately.
Well, it's just a thought that needs to be fleshed out...