From: Bremen, Germany
This is a flaw with the game, but to be honest, I use the same strategy. The French never thought they will lose the war against the Germans. So why would they sacrifice their navy?
I would suggest that the UK could resurrect a certain percentage of the French navy. Thus if you sacrifice the whole French Navy, then the UK will not get a chance to get the any of the French navy later. More of the French navy lost, lower the percentage the UK gets, in terms of getting any of the French navy.
I have not played the Allied side yet, but this refers to SC2. Depending of the British decisions, there should be a chance that Vichy France actively sides with the Allies. For example, if the British do destroy the French navy in operation Catapult, there is a chance that Vichy France sides completely with the Germans. This would be a nice decision event for the Allied side.
Many things were unthinkable before WW2, and now that everybody knows about them, we can't force anyone to do the same mistakes like they were done in history. That is a constant dilemma for every historical wargame. Example: The French thought the Ardennes to secure against an enemy attack. Hitler gambled and cut of the entire Allied forces. Today NOBODY would leave the Ardennes unprotected, and yet this was the most important key to the German victory against france.
I would go the Twillight Struggle way. Allow something, but add something bad to it. Yes you can of course move your entire French Fleet out of the Med Sea, bud if you do, there will be a civil uproar in Southern France and the French North African protectorates, so say good bay to x% National Morale or y MPPs because of civil unrest.
More or less something like what Bill did with the BEF Decition Event.
"You will be dead, so long as you refuse to die" (George MacDonald)