Logically the Germans should have required all the French Navy heavy ships to sail to French ports under Axis control as part of the armistice agreement dictated by Hitler at Compiegne in June 1940. That this wasn't done was a strategic blunder in hindsight. However had they done so the Frech might have simply scuttled the ships, as the Germans had done at Scapa Flow.
Assuming the French Navy was acquired intact the Germans have a problem in manning them - crew availability and training plus a total lack of familiarity in operating them. It is unlikely that German crews could operate them efficiently before 1941.
If France had changed sides completely and the French ships kept their crews and operated them as allies of the Germans then that completely changes the scenario. It also implies that Italian heavy ships, supplied and fuelled at French bases, would also be available.
''Give me a Ping and one Ping only'' - Sean Connery.