So, like a notification? I can see having messages like “House 3 is under attack!” being useful, but I guess the problem would be how the player would be reminded afterwards and be able to check their structures for damage without looking at every individual building.
Unless you meant a single icon for each structure or a list, notating some sort of damage to it. General workers/builder classes could then be automatically/maually set to recognize and repair these structures–possibly another tactic for the “Defense” tab? Workers get pre-designated to a certain area or list of “structures”, and would be tasked with repairing them or fortifying them during battle?
This could even open the possibility of activating multiple “strategies” at once–say for example, you have a town with 10 workers and crafters (military units are excluded). Four of them are “non-builders”, like Trappers, Farmers, and Weavers. These four could be set to the “Red Alert” command, while the remaining six would be set under the hypothetical “Repair under Fire”/“Bolster Defenses” command, focusing on their specific assignments. If the fighting gets too overwhelming, you could set all groups to an “All-Out Red Alert” mode.
(These are starting to sound a little tactic-oriented, so I might re-mention them in one of the tactics threads as well. I figured these ones related to the structure-recognition concept enough to keep them.)