Currency in Europe

Perhaps it would be useful if €group allowed their memberstates to issue a secondary currency, which would stand in a running value to the euro. The exchange rate of national currency to the euro would then ideally be determined by the ratio of economic output of individual countries to economic performance in the euro zone in a running rate ratio.
So the exchange of national goods and services could take place on the basis of the nation-state currency, while the cross-border trade within the euro zone happens on the basis of the Euro.
This would have the advantage of a less interference-prone monetary union.