What if the French were surprised in the Ardennes instead of ready for the German assault with everything entrenched, AAA and artillery fully manned? Instead of Germans disregarding reports that the French were ready have the French disregard reports that the Germans were coming. I have heard some say if the Germans weren't so mauled in the opening stages of the war they might have gotten to the outskirts of Paris before they got stopped. Personally I see that as somewhat fanciful.