I think that a War of Napoleonic succession would be fun.
Imagine: Napoleon dies in 1811-1812 and you have the Imperial Army split between those who support Joseph and those who support the infant Napoleon II.
Alternatively: Spain in the early 19th century. If Carlos IV dies and Fernando VII escapes, you could have a war of Spanish Succession between the French Imperial army, supporting Jose I, and the Spanish ragtag army supported by the British, behind the candidacy of Fernando VII.
Now that I remember, the Carlist Wars also count as wars of succession, meaning the last war of succession was in the 1870s. So perhaps I'm looking at this the wrong way.