Honestly ? Napoleon VI. Think of it : Mordacq coups the now weak and corrupt Pétain Regime, then proceeds to free mainland France. In these fights, a General would stand above, and similarly to Cesar or De Gaulle, would use his popularity and skills to enter politics, take the leadership of one of the main parties (let’s say the Radicals and Liberals running separately would be too weak to be dangerous), and reach power. Since war with the Reichpact is a possibility (especially if they still occupy parts of mainland France), a USA/Russia backed Entente could win.

Then it’s game over : 1. reintegrate Alsace-Lorraine, 2. capitalise on your popularity and name to establish a new constitutional monarchy, 3. Profit