A quick end to the war could get you a status quo ante vellum peace, alternatively a german victory before Christmas could also deliver that. Otherwise, I don’t see how A-L could remain in imperial hands. In either cases, France is either slightly or much more diminished as far as its influence in Europe is concerned, but it could do two things and succeed perhaps to a degree higher than IRL: either try to rebuild its influence and cooperate with the Teutonic masters of Europe, thus establishing trade pacts, customs unions and an enlarged Latin Monetary union so that the French economy can benefit, or wholly focus on the colonies and integrate as many as possible, while “abandoning” any ambitions in Europe. I think it could actually prove a good thing for France, if handled carefully that is and if it does not result in significant political unrest(which would be extremely difficult). If they manage to pull it off however, with far more frenchmen(as a result of a shorter war), France is more prosperous, more influential as well as richer today. Maybe that France can afford to mend fences and build bridges with a dated Germany.