Including convincing countries that would suffer economically from the extinction of the arms industry.

This highlight that you are thinking only according to how the system currently work (or how you are told it works). No country would actually suffer economically if they cut off the arms industry because they can use the money and resources for something else.

Countries are populated by people and humans can defend themself even without stealth planes or nuclear submarines. It’s the government that needs asset to exercise their power be it machines or people.