France, sadly, doesnt get that mcu haction in timelines not related to the World wars or Napoleon........
I've always been fascinated by the second French Empires possibilities myself.... I've got a TL in the works right now actually. Just a little preview, though it may die like every other TL I've attempted:
"The Empires on which the sun never sets"
A TL in which a rather more multipolar world, rather then the bi-polar German-British domination and a sidelined US eventuates in the late 19th century. Involves, somewhat ironically, the Second French Empire doing better due to Napoleon III being temporarily incapacitated, and someone/s or other(haven't figured out who yet...a major stumbling block) siezes the opportunity to create a semi-constitutional monarchy... Napoleon III remains/regains dominant position in the state, but is somewhat tempered..... thus some of his wackier foreign adventures are avoided, for example he is not allowed give anymore then verbal support to the Polish rebellion..... nor is he able to authorise that crazy Mexican intervention. Besides that, the military coup means that more funds go to the French army, which is reformed and reorganised some more.... while the French navy, while not built up significantly, is reorganized into a cohesive unit....
These reforms would probably be opposed by Britain, if it was done in peace time. Wisely, however, it is done under the cover of allying with Union in exchange for economic concessions and (limited)support in the intervention in Mexico(which is done with Spanish and British support, given that it only goes so far as to collect debts). In the end, this results in a slightly shorter ACW, a collapsed Mexico in which US, France, Spain and Britain jockey for inluence, a stronger French economy(due to the strong economic relations between them and the US, as well as a cheaper war), and a French Army and Navy that are stronger, better organized, and have a better reputation.
I'm still not quite sure how the Prusso-Austrian war will fit into this....