Gold can be hoarded which constricts the money supply/liquidity. Then lent at interest (usury). Gold is a form of wealth, however other forms must be available to prevent hoarding. In Promise Language any form of value is transactable: gold, silver, land, time, labor, yen, dollars, euros, etc.
No thank you. We get a huge advantage by being the single producers of the world's reserve currency. The two pillars of the American might are the dollar & armed forces. Our corporations & armed forces would suffer dramatically if we adopt some kind of equal currency with any friend. Not good for us.