I know there already a thread about rearming cost so not going to dwell on that. I think a new building called munition warehouse would be cool. The building would allow you to store napalm, fort artillery, mines, and mystic mines. It would cost the same to build them as it does to rearm them Although maybe a slight time like 5 minutes each. The warehouse would have a toggle rearm/store. While on storage you could just build up to fill warehouse Rearming manually like now. Toggled to rearm it would automatically rearm any defenses that it currently had stored after each defensive battle. Upgrading the warehouse would allow more storage.
+1 Not a bad idea..... maybe even tie it in as a Guild Perk to help reduce the costs of rearming mines when funded