Maybe the best way is for Napoleon to die of one of his countless diseases in 1807, before the Peninsular War, and the throne to pass to his son with a conservative marshal as regent...although of course that largely obviates RCTFI's original WI conditions.
Thande
Agree with the 1st part but as far as I'm aware his only legitimate son was the one by the Austrian princess Louise-Marie and he didn't divorce Josephine and marry her until about 1813.
If he had died earlier, then the question of the succession to the empire could have led to someone more willing to accept the independence of other powers and hence more acceptable to them in turn. However who that would have been and how much uncertainty and disorder inside the French empire would have resulted is a big question. Not sure if he had any recognised successor for the empire at that point. Suspect not.
Would be a very strange world as France at that point included large slices of Germany and Italy as well as what is now Belgium. Whether nationalism would have split it apart over time or they would have been converted?
Steve