Well when you don't have advanced missile defense or Air Fore, you have to resort to this. Otherwise your military capabilities will be heavily degraded and your ability to respond will be almost non-existent. In Gaza, there is similar underground 'cities', no such thing as 500m deep but intended to make arsenal mobile and protect it, it makes preparedness at a high level. However still during war it isn't easy to move weapons around since underground system still is lacking. Iran on otherhand has resource abundance and probably is able to interconnect many points it needs. In Gaza, war there is different case since strip is very small and not possible to hide any movement, in Iran this will be more worth the effort. My skepticism is regarding their missiles, ability to pentrate missile defense, damage radius, and quantity. I don't know what is needed to build ballisitc missiles and how many can be produced, for purely conventional purpose they need large quanitity. Or simple resort to chemical warhead.
