Then you’ll have to be careful who you choose as a host nation and what the agreement says. Even then, plan on limiting trade to approved connections, that can change with the global political climate.
My suggestion is that anything wanting to be called a seastead should strive first for self-sufficiency, as a matter of design, then worry about trade at a later time, when the ability to produce is proven to exceed internal needs.
My own, initial project is a yacht, aimed at proving some, not all aspects of my concept, while other portions are proven ashore. Once that is all covered, I plan a larger version, to combine all of those elements, and add multi-trophic aquaculture/mariculture, to show the commercial potential. Demo-scale out of my own pocket, and look for investors when I have something to show them, other than mere pictures on a computer.