+1 on the removal of .DT for enemy assets - it won't stop spiez and alts but it makes more sense than having down to the minute intel on when their hangers are going to pop.
+1 on giving HQ some kind of radar protection. The most strategic asset to your entire country is wide open - doesn't make much sense, especially if the object is to get people to up and defend HQ. No warning = no time for intercept.
I am still of the opinion that it would make sense to vary the radar ring size by the size of the airfield. 12 miles for small fields and vehicle bases, 18 miles for medium bases, 24 miles for large bases and CV groups. That provides a much more realistic radar defense and makes attacking radars more important in preparation for a strike to HQ.