If one day most of countries in the world ban BTC, will someone with a lot of money spend million or even billion of dollars to establish a whole country. In this country, you will exchange with BTC and other crypto. Will you leave your coutry and move to this 'wonderland'?
First you need to find a unclaimed land to make a country, And well there isn't a single piece of unclaimed land left on earth. So I don't think a new country can be established now.
But just to answer your Hypothetical question, Yes I would probably move to that country given that it has everything else that I have in my country, it can't be just a country using btc full of bitcoiners with nothing else like a country.