Can you give examples of where this has been tried before. Also, this sounds like how we were colonized the first time. Giving enclaves to the French and the British that became staging posts for full colonization
None have been built, although both Madagascar and Honduras briefly considered the idea. The theory is presumably inspired by Hong Kong, but obviously Hong Kong wasn't set up with any such purpose.
[1] https://en.wikipedia.org/wiki/Charter_city_(economic_develop...