Came across an interesting snippet of EU history a while back about how in early 1963 Franco-German relations apparently became strained due to price disagreements over the new Common Agricultural Policy (CAP) with de Gaulle actually threatening to withdraw France from the EEC. Now he was bluffing since he didn't follow through when the Germans called him on it, but for the sake of this thread assume that he was serious and did remove France from the EEC. Bear in mind that only three years later he would withdraw French military forces from NATO's integrated command, but not the alliance itself, as he felt he wasn't getting his way enough.
From a British perspective this is interesting as it was towards the end of that year the UK, Ireland, and Denmark had their application to join the EEC vetoed by France. Here if France has withdrawn then the applications are probably successful since as far as I'm aware none of the other member states felt the need to do so. Considering the similarity in population sizes and national economies this would have France and the UK effectively swapping places, an Anglo-German engine? Rather ironic considering recent events.
One of the main things I was wondering about was how does this affect the evolution of the EEC? Without De Gaulle there might not be an Empty Chair Crisis, conversely IIRC Britain favoured intergovernmental over supranational organisation so something similar and resulting Luxembourg compromise might still happen. I could see a much more capitalist and free trade based policies finding favour within the EEC. Does the CAP grow into such monstrous proportions or does no France mean earlier reform of it? The whole folly of Strasbourg is avoided. I'm guessing that France probably doesn't get allowed back in for quite some time, or at least until things are organised as member states want them.