Yea it's a pretty difficult line to tow especially from a CiC perspective too.
I think that's why there's penalties in place.
What you could do is the following:
Your a squad defending a base and T+60 rolls around, and your sure that your target hasn't been attacked. You ensure this by sending at least 1 pilot down to assess damage.
I know while directing frame 1, a squad contacted me and said that A2 was not hit and it was past T+60, however when I jumped over there, a hanger and radar tower was down. The attacking force had just snuck in under them.
So you have ensured your target is pristine...
Contact your sides CiC on 150, and then remain on station.
The CiC then can PM the setup CM, who can contact the opposing sides CiC and inquire about the situation.
If the attacking force was intercepted, was delayed, is just late....he'll know. He should inform the Setup CM if he intends to divert planes and if so, responds that an attack is coming or not.
At this point the setup CM can relay information to the CiC of the target, and he can make the call to shift the CAP someplace else for action. This ensures that everyone gets to have some fun, hopefully.
It should incur a severe penalty however, if the attacking CiC states that no aircraft will be attacking that base, and then some do.