I thought about trying a Vichy French and Italian Civil War situation, very unlikely of happening but plausible. Vichy France is easy, if Germany takes Southern France, all Vichy French comes into power. Southern France becomes the new capital, all original French territories join Vichy France, if French Indo China is under Japanese control by this time, Vichy France does not take control. All units on French territory join Vichy, all French naval units in the Med join Vichy France. Vichy France join the axis but becomes neutral.
Italian Civil War, if southern Italy is taking control by the allied powers, all Italian forces outside of Europe or Russian including navy join the allies controlled by the British, Italy must surrender all battleships and carriers to the allies. Italian forces in the North, Europe, and Russia remain part of the Italian Axis forces.