Most of these 'colony' ideas end in disaster. Attempting to form one in the open ocean, likely just speeds the process.
That said, a few Islands in the Caribbean pretty much act as private play grounds for the rich and famous, even now, don't they?
The guy who owns Virgin Atlantic comes to mind. And remember the sex fiend pal of Bill Clinton had such. Bill even visited his island, IIRC - probably to discuss how better his foundation could help the world's poor - I hope.
None of those examples are of societies basing their economies on bitcoin though. The basic problem I’m curious about is how does one enforce a judgement? Let’s say I don’t agree with a ruling against me and I’m just not going to pay. What can they do? Expel me? Even then I still don’t have to pay.