Paper money replaces not only gold, but also any product, any material values that can be exchanged in the state. Therefore, paper money at their face value is stamped on the amount of increase in gross national income of the state for a certain period.
I do not quite understand the reason why the Bank of the Netherlands is concerned about the possible general collapse of the global economy. In my opinion, this is too much exaggeration. Problems in the world economy have always been, however, they are completely solved by conventional methods.
Not that much exaggeration, actually conversion of world currencies to one universal crypto will induce negative effect to the economy of the country. No standard will determine the price and economy, if one country will have the currency of the world, they couldn't bare to handle the changes abiding these. In that regards, if the entire system collapses, crypto will not be the most accurate solution, it is still the fiat by each and every country.