Have these people never played BioShock? This is basically the same naive libertarian ideas going wild.
For such an project to be successful you need to have some serious funding. Why should anyone fund this?
Any legitimate industry will have a hard time on the ocean where you have horrible logistics, nearly no access to resources and are miles away from potential clients.At best I could maybe see a niche for some gimmicky tourism.
So what would it be used for? Let's be honest: Tax evasion, human trafficking and gambling.
It would be way too expensive to live there for normal people. Plus it would more oppressive. You can at least flee from a tyrannical government on land. If you are in the middle of the ocean? Good luck.
Though I dig the futurism. As long a they keep larping, good for them. Just hope they don't think it is a good idea in real life.