Maybe your plan is only to let the smart people join you, and hope they will all agree? I think that sort of plan is hopeless, both in figuring out who are the smart people, and then in getting them to agree. Intelligent libertarians disagree about large stuff all the time.
Intelligent libertarians disagree all the time, the difference is they don't resort to violence or coercion to force their views on others. It's the whole point of creating a truly free society like the Seasteading movement is trying to do.
But seasteading also (theoretically) uses new technology, which makes starting a country radically cheaper the way Moore's law and open-source software make starting a company so much cheaper.
The French Revolutionaries, Edmund Burke, Karl Popper, and others had thoughts on this issue which are relevant.
Whether you want sea steading to have philosophical relevance or not, it does. Which side of this particular debate do you think it is on and why? Do you see that as a problem or a merit?
What Thiel is saying is that the chance evolving the current system into something even vaguely libertarian falls somewhere between extremely unlikely and absolutely impossible at this point. Maybe there's room for arguing that evolving the government is possible, but the natural course is growth. There are few (I can't think of any) historical examples of government moving in the other direction.
If evolving the current system is ruled out, then considering something as revolutionary as starting from scratch like the seasteaders, while maybe less than optimal, doesn't seem so far-fetched either philosophically or morally.
Edmund Burke: Reflections on the Revolution in France (long out of copyright, you can google for the full text)
I am not trying to compare sea steading to storming the Bastille. I'm trying to point out that your ideology has a lot in common with theirs. You seem to agree with me that the French Revolution was bad. Great. But that does not remove your commonality. I urge you to take your similarity to them as a danger sign, and to learn more about it, and to get a clear idea of where you think they were right and wrong, and how you will do differently. A plan like "Well, I just won't use violence" is not good enough. Many people involved in the revolution did not want or intend violence. It happened anyway. Why? Because utopianism leads to violence, and because our society has knowledge and institutions that prevent violence which should not be destroyed or abandoned.
I also think you should consider carefully what is preventing reform in the US. It is not democracy, which Thiel seems to think is his enemy. It is not the Government. If enough people want change, they can get it. (In fact they just voted in a President promising change.) The real problem is people with bad ideas, isn't it? If only most people had better ideas, change would come quickly.
The only reliable way to deal with bad ideas is to learn how to persuade people of good ideas, not to start over and try to exclude everyone you judge to have bad ideas. (And what happens if some of your kids have ideas you consider bad? Or some existing members of the society change their mind? You will need persuasion.) Attempting persuasion has the added bonus that sometimes you will find out you were mistaken, not the other guy, and change your mind.
I suspect that people would join such a regime for religious reasons. If you're the only member of your congregation who chooses not to be punished for having a beer, not having a kid, flipping a light switch on the Sabbath, etc., your peers may take note and decide you're not really serious.
Churches would probably become jurisdictions, rendering that kind of mismatch moot. And hey, if some people require that much institutional pressure to avoid addictive traps, I'm certainly not one to argue (as long as it's not forced onto others).
Who sells what to whom?
Essentially, they would enforce voluntary constriants on future actions, when those actions are made possibly by access to information known by another party. This amounts to a property right, though like our current property rights regime, it is relying on a legal fiction as a useful abstraction.