What's the advantage you get from even more currencies that you don't get from today's basket of international currencies? The only one I see is that, if you build a big enough reputation to issue your own currency, you get to collect seignorage.

In exchange for that, you now have to carry n different currencies to make sure you can buy gas at a Shell station and an Arco; small retailers go out of business because they can't afford the overhead of combating so many varieties of counterfeiting--which, while still technically illegal, is much harder to prosecute--medium sized retailers go out of business because of the accounting overhead of setting appropriate prices when several currencies could be undergoing hyper(in|de)flation at any time.

I'm not sure that's a good trade.