Pertaining to your first comment that is indeed permitted under UNCLOS if you are talking about international law. However, under international law the artificial island will not get territorial waters which are 12 nmi or an EEZ which is 200 nmi. Don't quote me on this but I believe these created island would only get 500m of protection from the baseline. T
After what happened to Elwar, it's not a case about distance but about from who you are 12 miles away..
While I doubt the danish navy will start firing cruise missiles at you, Thailand we already know how it deals with this and I think both cases like Somalia or Iran would be clear no.
But that aside, the biggest problem would be to convince poeple to move there, and the reasons are pretty simple, why would somebody leave their country for this? All these types of projects have attracted millions of tweets and thumbs up but almost no clients.
Just because it's a country or small nation full of poeple who like Bitcoin it doesn't mean it will be heaven on Earth, you can see even in this forum we're not all friends, we have different opinions, we have different views on the economy or society, not even mentioning our language, culture and many other small things that would lead to poeple calling it Babel's Island.