Not how you're thinking, Cyb. If Germany breaks through the Maginot Line, or Italy breaks through in the south, or even France pushes into Germany, the French will still keep divisions double stacked on the Belgian border when they're urgently needed elsewhere.
Not to mention the fact that belgium is doing the same thing with france...and holland is doing the same thing with belgium. They can't do what they want to do with the engine, they want beglium and holland to sit idle while allied with france which just can't happen, the game makes the allies all dow. So the downside is having an AI that has to line up against a future ally because it doesn't have a brain. Happens everywhere, but the maginot line and the russian/manchuria borders are the biggest situations that shine a light on it.