That's off the chart idea. You can't just hold any island out there as all of them will be ruled by next government present nearest to that land. For example if it is in western Pacific Ocean then it is most probably under the rules of USA while the islands in the eastern Pacific Ocean would be under the territory of India. So you go anywhere in the world you will have to face the legislation first to acquire that particular island. It is good idea but bitcoin is not that powerful to get you island as government should accept that particular currency that is bitcoin to let you buy it. It seems to be complex idea and may not be possible at this point.
Bitcoin legalization or adoption in these countries has been seen as a triumph for the digital asset it may say less about the potential so far opinion on bitcoin and other digital currencies tends to vary from country to country while some are considering various forms or legalization others are either denying it existense or looking for ways to crack down on the coin the most recent positive case is the Philippines which is reportedly preparing the legalization of Bitcoin through regulation