I comletely agree with you. That is also what Vonmiser and I concluded. If more than one currency have to compete, the threat of Copernicus' law is unleashed as long as they are fully interconvertible without taxes, penalties, and inconveniences as Vonmiser stated. This alleviates the need to obsess about currency supply and who controls it. In fact, it obviates the need to obsess about what form and shape the currency has to have and that was my point regarding Bill of Credit, which are just another IOU. If there is a hard money anchor to competing currencies, however, price and value are teathered together in an oscillating relation, elastic yet restrained at once and that is, in my opinion, the most elegant of all solution.
What we know from history is that it is quite easy for rulers to devalue currency, even gold. However, what we learn from history is that the people will hoard good money and let bad money go and that means bad money, like a boomerang, ends up back in the vault of the bank or the king where it was forged and counterfeited. The common thread of monetary history is the suspension of redemption which rings in economies' demise.