1. The Germans never wanted to give up the mark. They were talked into it by the French, who viewed it as an essential part of the effort to build an “ever closer union.” To the German people in 2015, an “ever closer union” almost certainly means a “transfer union,” and they don’t want any part of it. There is no reason to continue to pursue a dream that is already dead.
2. A new mark would undoubtedly soar in value, thus making the population wealthier and imports much cheaper. This would create a substantial stimulus for the EU as a whole. The remainder of the EU would have a euro with a lower value, and would be able to increase exports and growth and ultimately reduce debt.
3. Any moral obligation to bail out the overspenders would disappear.
As far as I can tell, the only reason for the Germans to stay in, other than mere inertia, is that it creates a platform for them to impose their values on the rest of the EU. The potential consequence of that will be discussed in a future post.