Flag of convenience for ships and airplanes -- millions and millions annually. Mongolia has a huge merchant fleet. Thousands of commercial airplanes are registered in Bermudas.
Own top-level domain name -- if they will get creative naming their country they may land a popular domain.
Driving licenses -- Would love to pass all the rigorous tests to get an extra drivers license which I could use when traveling abroad.
Passports -- assuming they will implement all the necessary measures to filter out crooks, they can start offering 2nd citizenship. Second passport is super valuable to those who travel a lot.
Orbits and space in general -- valuable resource!
WTO quotas and re-export -- uh, oh!
Etc., etc., etc.
Becoming a recognized country opens a lot of opportunities.
They just need to crowdsource a few more billions and persuade neighboring countries to recognize them.