I have run into this problem at work. The logic, "it is done that way because it was always done that way."
I say tie it to fuel and leave the supply and hardness the way it is. It works for other strats, and the only big stink with HQ, is the negative impact on finding fights and causing players to loose interest and log off.
Fuel (to be clear Floob, I did suggest no drop tanks and 75%) limits would be an adequate reward for flying long, possibly dangerous mission to HQ. As Latrobe pointed out SOME folks would hardly notice, and I am sure that some folks would just about hit the roof in disappointment over limitation of their aircraft choices (see any ENY thread).
The logic of connection of HQ to radar, should only affect the information received from HQ via maybe telegraph, or some other wired connection. Otherwise all the radar towers are still operating fine (unless also damaged by enemy attack).
So, the immediate "lights out" for the entire country is NOT anywhere near as logical as "rations" for fuel until supply line has been re established.
IMHO, "lights out" across the board should be a thing of the past, even for short periods of time. Many days a few minutes to log in and have fun is all that is available. the last thing that I want to do is see a barren looking map.
Killing DAR is killing potential FIGHTS (note I will kill a radar tower for that purpose, only when I see there is an attempted mission to that field).