Let's say that the Kapp putsch or some similar military overthrow of the Weimar regime in 1920 was successful, and the new military regime repudiates the Treaty of Versailles and refuses to pay reparations or abide by the disarmament clauses. The new regime thinks they can do for Germany what Ataturk is doing for Turkey, but their attempt instead results in a Franco-Belgian invasion of Germany that sees the French and Belgiums in Berlin by the end of 1921. Poland has also taken the rest of Upper Silesia, as well as Warmia and Masuria. Due to an incredible amount of foresight, the French come to the following realizations:
- France cannot force Germany to pay reparations without occupying Germany
- France cannot occupy Germany forever
- Once France stops occupying Germany the Germans will eventually begin to re-arm, and France might not be able to stop them
Because of these realizations, the French decide to replace the monetary reparations with territorial compensation, and don't bother trying to enforce disarmament due to the belief that if Germany loses enough territory its economy will be too weak to support an army that can challenge France.
So let's say that the French set up a puppet Rhenish Republic that includes the Ruhr, and either annexes the Saarland directly or gives it to the Rhenish protectorate. France doesn't directly force reparations out of the Rhineland, but binds it to France economically in a way that ensures wealth will flow out of the Rhineland and into France. Does losing its best industrial zone cripple Germany to the extent that it could never challenge France again?
Also, how plausible would it be that the French supported an independent Bavaria? Since France can't occupy Bavaria, Bavaria would only stay independent if the locals continued to support independence. Would they? Or would the call of Pan-German nationalism prove too great?
I don't think Germany without Bavaria could pose a threat to France with the Rhineland at all. But could it head east? Geography would make it very difficult for Germany to threaten Czechoslovakia without retaking Bavaria at the very least or even Austria. But what about Poland? If France was for some reason unable or unwilling to intervene, how well would a Germany without Bavaria or the Rhineland fare against a Poland with Upper Silesia, Warmia, and Masuria?