There are a few threads on this forum concerning the possibility of a Franco-German war in 1905, where the Germans decide to take advantage of Russia's problems to have a one-front war with France. I think it is fair to say that the consensus is that such an effort would fail, because France, at that time had a defensive strategy.
So my idea is to do the reverse. Let's say that Germany and Austria, after the Battle of Mukden, decide to settle accounts with the Russian bear at this most opportune moment. Germany leaves as minimal a force on the French border as it can get away with, and then Germany and Austria send everyone east as soon as logistically possible. This also gets around the ammunition production issue, as Britain would not be in the war and thus the Germans would not be under blockade. What happens?
P.S., if you think this is a bad idea, at least its not another Sealion thread!