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?