I suppose one could have the Euro circulating alongside freely-floating national currencies. The value of the Euro could be constructed as a currency index. The system wouldn't be vulnerable to attack on the financial markets, but I think people across Europe would still find it inconvenient to convert back and forth. Can the last politician to go out the revolving door please turn the lights off?
I'm interested in the concept of a new Euro as a "European energy unit": in energy grids across the Baltic and North Seas and across the Mediterranean, both of which already have the initial elements in place.
National currencies?
Simply base them upon property rental values, as John Law envisaged three hundred years ago. "Any economic unit can emit money. The serious problem is to get it accepted" Hyman Minsky
As an economy is in transition then GDP per dollar of energy consumption has decreased over time-including in the USA.
But, keep working this through... Rutherfordian ------------------------------ RDRutherford