I have my doubts that the German Mark would be stronger that the Euro even if the 2 co-existed. German industry would lose a lot of business. In times like now, when costs are an issue, even a 2-3% exchange rate fee and 5-6% exchange rate risk premium would put German business at a significant disadvantage. Yes, there are a load of eastern European businesses operating competitively without the Euro, but they all have much lower costs/wages than Germany. UK industry has suffered by exclusion from the Euro, German industry will also.
Your comment is deeply flawed here. If you observe the EUR/USD FX rate at times of German economic news releases you will see that it significantly impacts the rate, so what happens Germany hugely influences the exchange rate.
Considering the global economic difficulties (to put it mildly), the German economy, especially exports, is doing very well. This resulted in the strengthening of the Euro in the months up to the time when Greek debt problems fully emerged. Now, if Germany left the Euro, the Euro would no longer be propped up by German industry and fiscal frugality, thus making the Euro much weaker, and a D-Mark stronger. Add to that the fact that the German central bank would take it's currency reserves with it, which make up 33% of Euro gold reserves, and the D-Mark would be much much stronger than the Euro.
German industry wouldn't suffer much, as German products come at a premium anyway. Consumers don't buy German made products because they are cheap or cost competitive, but rather for their perceived higher quality. Any loss to the German export industry would be a gain to the import industry, especially oil and gas.
To be honest, there is absolutely no danger of the Euro breaking up - all we get is a series of tabloid headlines with no substance behind them. While you may get the odd gripe from the tabloid press and certain political groups in Germany, there is no appetite among the ordinary German punter to leave the Euro.
I agree that the way the British media has covered the possible collapse of the Euro is sensational, and all they are trying to do is make sterling, which is a lot lot weaker than the Euro, look better to the public. However, just because they do not adequately back up their claims, does not mean that there are no good reasons.
While the Euro gained popularity in Germany, it initially was very unpopular. Stating that there would be no public appetite in the German public to leave the Euro is unfounded, and it won't take long to **** the German taxpayer off enough, if the other PIIGS countries come looking for money too.