So, I always think of the HQ as just that, Headquarters and it has little guys in there that provide communication between the bases. As if when you are over the base and you don't have radar in your plane, (aka WW2), then HQ would call in with enemy positions about bases to the tower over your own friendly base, who would then relay the information to you via radio. While you are over your own base then your proximity base tower would relay enemy positions also to you on the radio.
Therefore, if you understand that, I would like to see countrywide dar continue to go down if the HQ is flattened, but, your proximity base would still have local radar and the ability to "radio" you reports on their position.
Clarification: Take down the HQ and dar bars are gone, but if you are within the circle of friendly radar, you would have dot dar for that base only. Fly to a different base and as you enter the friendly radar ring the enemy dot dar pops up for that base.
Thank you