For this thread we're assuming that the decision to attack Russia first is made several years in advance (say 1911 at the latest). Whoever is in charge reasons opposite to OTL, thinking that Russia is the bigger threat and needs to be dealth with ASAP, more so since Austria-Hungary will not be able to resist Russia for more than a short time on its own and because Russia recovered fast from the RJW and will mobilize quicker than the six weeks that Von Schlieffen anticipated, leaving Germany's long eastern border vulnerable. On their border the Germans build border fortifications. The war still starts in 1914.
Now here is the question: Would the French, if they bash their heads on the German border long enough, try to outflank the Germans and pull a reverse Von Schlieffen? Could they become desperate enough to do that?
I personally think it's unlikely. Any chances of Britain joining them to help will be rendered nil and Germany will gain another ally or maybe two (Belgium and perhaps Holland if they feel threatened). What do you think?