Always bugged me that when captured, everything invested in taking the city is lost: ships, planes, infantry. What if you have a land, sea, or air patrol configured to emerge from and return to, span, or encircle a city? Shouldn't that ameliorate destruction? The city might be captured, but some infantry or a troop transport anchored within may escape and be applied toward an insurgency to recapture it. An incentive to patrol your important cities?
I always loved setting up an 8-plane radial patrol from my AC's and having them cruise past an important city. Used fast moving 3-space destroyers for patrols too.