This problem of multiple notes is exactly the hell the Euro faces in January. There is a pretty good special section in last week's Economist about the sheer difficulty of moving coins, bills, managing multiple tills, etc. The more these governments screw up, the longer they take to exchange the currency, the more old (and subsequently valueless) cash the people will be stuck with. The transfer is supposedly going to take only 30 days. Can you smell the scale of this rip off? Note that your VISA card doesn't have that problem. My first thought is that the problem isn't the currency, it's the use of physical exchange media consisting of coins and paper.
I don't think multiple exchange media will work very well without EFT (electronic funds transfer) but this looks like very fertile ground for some clever inventor who could come up with something better than paper and coin that could do the trick. (That's the cogitating part.) "Coming up with something better" could be tough, but I don't see it as at all insurmountable. It took a long time for people to accept paper (and some are still bitching about it as we see here). The key is that it is useful, decrementable, secure, private, easy to use, and tamperproof without need for an instrument. In that respect, we might well see multiple exchange media used in specific sectors or locations with the currency exchanged at the door, much as we see tickets and tokens at amusement parks.
It beats stuffing penny parking meters with gold coins.
No one, to my knowledge, is objecting to fiduciary paper currency -just to fiat currency. In fact, most of the gold people are perfectly in favor of over issuance of this paper - as long as holders can redeem. I, OTOH, have more rigid requirements before I'm happy.
PLEASE POST A LINK TO THE ECONOMIST ARTICLE OR GIVE THE TITLE