The currency aspect struck me. It would depend. The world could manage well with a single currency, if it wasn't centrally controlled. As soon as it is, then it reflects the values/agenda of the controllers, which won't coincide with the entire planet.
Greece is a good example. Germany manages the euro, but is a culture that has had to adapt to strong seasonal variances for millennia. Greece, being a mild Mediterranean climate, is able to pace themselves. What happens when one controls the fiat of the other? It simply doesn't work. Adjustments for culture cannot be made on a macro scale from a central control.
But if it's a currency such as gold, silver, bitcoin, etc., then there's nothing stopping it. It is not managed. There is no central bank cartel that everyone has to bow to in order to do business.
Thanks for the provocative article.