....
- don't move a finger until spring 1941 - no provocation at all
This is a bit extreme. The Allies had a assortment of 'appreciations' and 'outline' plans for periphrial operations. These also included limited operations in the west. The rest of your OP does fit Allied expectations.
And then, somewhere in 1941 (summer ? fall ?)... the Entente Cordiale starts an offensive against Germany.
Does anybody knows about the plan, if ever ? is there a TL somewhere exploring that whatif ?
Any chance that would ever works ?
Yes, I've had bits cited to me by French historians and amaturs. Apprently no English language historian has bothered to investigate it, tho a few like Chapman or Horne refer to it vaguely.
If I am reading these fragments correctly 1941 was to be a year of escalating limited attacks, around the edges, and on the Franco/German frontier. The main attack may not have come until 1942, which seems to be when French remarmament would be complete, and when the German economy was calculated to be in the toilet. Of course had Germany fallen apart faster the French would not have been adverse to acting sooner.
In this ATL superficial references to French "Doctrines" of the 1930s & 1940 are largely irrelevant. First the principle guilty party, Marshal Gamelin, was headed for retirement before disaster struck in May 1940. The French secretary of Defense had never been a strong supporter of Gamelin and had decided his 'Use By' date was past. It took some months of political manuvering, delayed by a illness, but Gamelin would have been on the retired list in June 1940 had the Germans not struck.
Retiring Gamelin opens the senior ranks of the French army to a new generation of generals, and a acceleration of change in doctrines from that of the conscript army of the 1930s to something appropriate to a fully mobilized, equipped, and trained army of middle 1941. The French army would not develop some version of the blitzkrieg fantasy. It would probablly have a resemblance of the US Army in Europe of 1945 with a balance between firepower and manuver, and more tanks that Guderians wet dream.
More important is the French had planned for a massive air force by 1942, of the most modern aircraft available. They had their estimate of German production capacity, and intended to match that with their industrial reforms, and drawing on US industry. With the RAF the French leaders intended to overmatch German air strength by a considerable margin.