There should be a mechanism in place to allow you to pull out the gear from a siege and put it on a person before the next attack happens. or just fix the item bomb issue with gear not be accessible.
This clearly didn't happen with the issue in this thread, but if I was in a city that was getting attacked wave after wave, and the only way to get a reprieve to get gear out, was to attack the city yourself, I would certainly do so. "Sorry, gonna have to wait another 24 hours so we can actually use all of our equipment" seems pretty reasonable. But this strat has a lot of issues that need to be worked out, and item bombing has been around for multiple strat versions and still isn't addressed.