They would wind up eating the debt anyway as their customers went under.
France has never been able to compete on German terms; another export nation, but it has retained a large or at least very influential agricultural sector. However, based almost purely on political motives the French have tried to first create a hard Franc, and then the lure the Germans into the Euro. That was part of the deal made between Kohl and Mitterrand for the German unification.
The French have gone along with the Germans building a pan-European (or rather a pan-EU) Bundesbank, free from political influence. However, at the same time France's long term plan has been to eventually take over the bank and make it run by the politicians. France has always known how to bend political agreements to its will. (Sarkozy has been surprisingly open ever since his election that this is one of his primary political goals.)
So, if the present political turmoil really turns into a big currency crisis in the eurozone, the French certainly are going to do their utmost to create a political solution that would keep the defaulting countries within the Euro. The German government may go along to a certain degree, but since it will be the Germans who will have to foot the bill, the 1 000 000 question is for how long will the Germans act contrary to their own interests?