There is an SEA setting where dar bar/radar is only visible to those in the tower. What about implementing that when the HQ goes down? otherwise, i don't think there is a game setting that only enables dar/bar on a local level for the immediate base and sector you take off from. I should think that with an HQ down, country wide coordination should be disrupted - but not so much on the local level with a functioning field radar.
I also like reducing/halting the resupply chain to friendly bases.