Suppose Napoleon I wins. What happens with England? Napoleon had installed kings all over Europe - Bonapartes in Spain, Holland and Westphalia, Murat in Naples - but also added a lot of departments to France. What was going to happen to British Islands - installing a king, or annexation to France proper?
And who out of Napoleon´s family and henchmen were available and eligible to be King in Great Britain?
Also, what shall happen in May 1821? Assume that he was not murdered, and therefore dies by stomach cancer on schedule. The King of Rome is still 10 in 1821. The constitution of French empire provided for regency, should Napoleon die and leave underage heir. But in October 1812, when Malet claimed to be appointed dictator after Napoleon´s plausible death in Russia, nobody proclaimed Napoleon II emperor and regency as provided for by law... who will become Regent for Napoleon II in 1821?