It would be interesting to see what would happen if Vichy had still been in existence as of spring 1944 and had not been incorporated in the 'Reich' earlier - presenting Hitler with the dilemma of what to do with a supposed ally/ puppet government who could defect as a 'rescuing' Allied army approached, as with Rumania and Bulgaria on the Eastern front in 1944. Should the Germans strike first and occupy the country fully, as they did with Hungary in real life to depose Admiral Horthy, or leave the country alone and risk it defecting and having to be reconquered, as occurred with Rumania when King Michael deposed the Antonescu regime and switched sides and the Germans then bombed Bucharest before the Red Army could get there?
Might the military and financial strain of occupying Vichy as well as northern France cause the Germans to hold off attacking it until it was too late and the Allies had landed in June 1944, then face an anti-German coup in Vichy itself and have to combat this in an equivalent of what actually happened in Rumania? The senior politicians and generals in Vichy could insist on the Allies giving a private written pledge of no war crimes trials etc in return for their action, and hold them to it in 1944-5. Or would the Germans occupy Vichy in a pre-emptive move against defection after the Allies had overrun southern Italy in 1943? In either case, we would probably have a civil war in Vichy and a diversion of German troops there to prop loyalists there up. If this was in the run-up to or after the Allied landings in June 1944 it could cause a quicker German collapse in Normandy. If it is in the months after the Allied landings in Italy, do we have the Germans moving troops from the Balkans to defeat the 'rebels' as this is a less vital front than the N French coast, Italy or Russia - rescuing the Allied campaign in the Aegean from defeat?
If the 'pro-Allied' side won a civil war in Vichy in June-July 1944 (by means of reinforcements landing on the Southern French coast from Italy, earlier than the OTL landings on the Riviera ?) or fled South to hold out successfully in the Rhone delta/ inland Provence until Allied landings, we have the prospect of this part of the Vichy government structure salvaging some of its reputation for collaboration. After the Allied victory there would be even less appetite in Paris for a large-scale purge of 'collaborators', even those who had been deporting Jews in eager not reluctant alliance with the SS. The new government would be keen to acquire more support against the French Communists and their Resistance guerillas, and the US would be keen on this too. They could present and insist on a public 'narrative' of the majority of Vichy only assisting Germany out of self-preservation and a 'heroic' group of senior figures fooling the Germans in 1940-4 and really helping the Allies, though logically Petain himself and any other senior figures who failed to defect quickly to the pro-Allied revolt could be sacrificed as scapegoats. So logically we would have an even more contentious question of who to punish and drive out of politics post-1944, and the Left raising cries of a regime 'fix' to let pro-Germans off. And the presence of 'moderate' Vichy figures who had defected in 1943 or 1944 still in French governments in the late 1940s, while the Vichy archives containing papers on their help to Germany
that could embarrass them were quietly destroyed.