It would have to be a country... as any country we tried to do this in would steal everything we had in the name of justice or terrorism or really w/e as the masses are really stupid and believe anything.
I think it should be an enormous floating Bitcoin city, that could travel the open ocean. If these could be feasible and repeated the world would avoid overpopulation issues.
Like the guy who made a floating island out of empty bottles? a few miles wide of a bunch of old cans and bottles could make it happen. Sign me up.