What could actually be done and be successful is a 4 Phase, $55 billion plan to use some of the world's empty islands as a buffer country.  while not cheap the money is from investments, loans, self-financing and other sources.

The updated original document is in the link below.    A Phase 0  working document is being developed to further define and refine what is in the attached document.   It is currently over 105 pages long and  is backed with over 20 gigabytes of data.

This is here as a rebuttal to the "Refugee City" idea that was doomed to fail mainly because of the fact that it is a solid structure refugee camp and not a self-reliant entity.