It also looks a little like those countries with their own national currency but also everyone accepting USD. Tourists can carry dollars, lose a little by unfavorable rates at every payment, maybe end up with change in the local currency to use in the next shop. I remember that on vacation in Uzbekistan.
[#] This is a well-known social/evolution dynamic: group selection. Bees suicide when attacking: individually it's a weak behavior, but globally it makes the group more resilient. The balance between cooperation and competition is a balance between individual power and group power. Europe is a group of groups, so the balance is weirder but having too strong cooperation at the top level (eg enforcing a common economic policy) will weaken countries. But only some countries because of non-homogeneity, thus destabilizing everything by lowering local national resilience (to specific local concerns, which do exist). So i believe we have to accept that we need slightly stronger countries to make the european union stick together.
...
But thinking about currencies and economy in europe is always kinda doomed because the euro is double-locked. No national economic policy actually has a meaning since at most your gonna leverage some power to influence the ECB, but you're never gonna be the one to actually decide. So there is a complicated combat to do cross european countries saying ok we have to re-found the mission and the organization of the ECB, the relationship with national economies. How do we want to keep down inflation: just maintain growth in face of other world economies that actually grow or make ourselves more independent, what do we do when countries have diverging interests, how do we make sure it's regulated and we keep control on it?
I would vouch for a system where euro exists but is restricted to cross-country corporate business and easy traveling: common credit card system where you can transparently withdraw any participating national money at the current nation negociated exchange rate (eg federating by having a star topology instead of a complete graph for exchange rates: "we treat all the others the same"). Additionally the BCE should have a second decision instance (two-chamber-like) basically being the european budget commission but elected by people, not chosen by governments, to ease cross-country political action. And on a more technical/practical level we have to rethink about wire transfers. I don't know much about how SEPA works but it's probably interesting to take a look.