Perhaps it’s not opt out in 1st world country, but some other country that offers this as its social contract. Or Australia could offer a nation state-within-a-state opportunity (say, offer to sell a 10,000 square mile tract of Australia w/ a little seacoast and lots of desert along the southern bite). Consider it a form of leveraged-buy-out. Pay for it over, say, 100 years with an option to pay off early. This would be all “new” money to Oz government coffers. Where the fees cover defense spending initially until these willing-to-depend-on-only themselves can build their own deterrent ability.