I will be brief: it’s a bonkers idea.
I agree
I see no reason to do such a thing, there are already countries, cities, towns, villages why not focus on convincing these people to use bitcoin as a means of payments and investments? creating an island and taking them away from where they live to go live on an island, I don't see how that could be good. who would leave his house, town, friends to go live on an island just because he's a bitcoin fan if he can be in his house, in his town, with his friends and be using bitcoin?
Well because said countries will never give up their power over currency nor will they allow their citizens to live free or truly own anything. I mean we all have opinions and many would not want to come but I am sure there are others that would willingly do so given the current political climate.