Such a decision to advance into Germany would have had to be taken at the highest political level. Not by a mere military commander.
Ooops! What am I talking about? Such a decision was taken at the highest political level. We decided to sit on our hands.
How about; what if France had got off it's backside when Hitler re-militerized the Rhineland? Would the Wehrmacht kicked Hitler out of power?
Or even; what if the Queen had bollocks?
Oh yeah, she'd be the King.