A third way would have been success at retaining the alliance with Belgium. That leads to a better Belgian defense, plus the French army reinforcing the Belgians from day one. Instead of being parked in the norther provinces and rushing north is some kind of race the French move in a organized fashion in September 1939 & are deeply entrenched in depth when the Germans do attempt to attack. As it was in 1940 the Belgian defense and its fortress program were flawed by internal politics and several extremely difficult operational or strategic choices. A closely coordinated defense policy with France from 1928-1939 can create a fairly solid defense.