In my opinion, the idea is not bad, but it is doomed to failure. All parts of the planet have long been distributed among states and are controlled, and this will already be a violation of rights.
If they collected enough fund they can just buy these pieces of lands and own the rights on that property. I do not think that this kind of thing will bring a violation of rights as long as all is processed in legal ways. We do not need to barge in and say we own this land, we can just all act as a responsible law abiding adult and buy land that is owned by other people if they agree.
Every property comes under some form of government ,so it is an impossible task,OP is planning to build an entire township and have his rules imposed other than that what is the real use,if he is the sole habitat in that island,that does not make any sense either.

There is no restrictions to use bitcoin so what is the problem now,he could accept bitcoin for his business can trade and you can have all the freedom in the world with bitcoin even now.
Yep, totally agree. It would be pointless to make state of bitcoin, if we could call it that. I mean it is an interesting idea, to think that there would be an island, where only bitcoin would be used as an currency. But with current situation it would be impossible, because of high fees and low transaction fee. Maybe in future, when more people start using bitcoin.