An interesting idea but the whole point of a passport is to prove which country are a citizen of. Countries set their visa policies to accept or deny based on passport origin. A US passport can get you a visa quickly in most places in the world but a North Korean passport would likely not. If I can simply pay for a World Passport, what incentive do they have to diligently verify my documents? Obviously a country could produce fake passports for their own citizens but that would be for some specific reason like espionage. Maybe a small country would produce a passport for me with a big bribe but I'm guessing the countries willing to do so are at the bottom of the list of "most accepted passports". Allowing anyone to get a passport with little scrutiny just devalues the passport. Perhaps in a more enlightened time, something like a UN passport would allow stateless people to travel easily to countries that would accept it.