This was inspired by the long-running Male Rising timeline.
Challenge: With a POD after the OTL fall of the 2nd French Empire, have a World War I analogue with the following sides: On one side would be France, Austria, and Russia, and the other side would be Great Britain, Germany, and the Ottoman Empire.
Bonus points if you get Denmark, Sweden, Spain, and Portugal in the war too.
I won't try to crank a whole timeline, but I'll offer some suggestions for events that could have rearranged some of the OTL alliances as required.
First, France and Britain were not allies until the early 1900s, and even then it was a tacit alliance until WW I. Britain and France were nearly at war over the Fashoda incident of 1898.
The subsequent reconciliation required some skillful work. Edward VII did some of it, by making a state visit to France during which he ostentatiously praised everything French. But the whole thing could have gone the other way.
Second, Germany and Austria. Austria became allied with Germany, which had been its enemy, for a lack of any alternative. Many Germans regarded Austria as a failing state that was a drag on them. Pan-German nationalists openly wished for the collapse of Austria, so its ethnic-German territories could be added to Germany.
Suppose that Franz Josef died and was succeeded by Rudolf (obviously before Mayerling in 1889). Without FJ's patriarchal aura, Austria-Hungary comes even closer to breakdown than OTL. Now suppose that Pan-Germanists in the German government try to precipitate the collapse - perhaps by sabotaging renewal of the Austro-Hungarian
Ausgleich - and get caught. The German plotting extends to sponsoring violence, which backfires magnificently when some radicals connected with the German operation assassinate Rudolf. Now Germany is a known enemy of Austria, and Austria turns to Russia for support, with the relatively slavophile Franz Ferdinand in charge.
Russia, about this time, is marching against Turkey. Britain supported Turkey and prevented the complete triumph of Russia. Britain is paranoid about Russian plots against India. Germany, which is now at odds with Russia and Austria, also helps Turkey. Austria joins with Russia against Turkey. Italy has revanchist ambitions against both Austria and France, and maintains its alliance with Germany, and also allies with Britain, with its powerful Mediterranean fleet.
Wilhelm II marries a different wife, who is not anglophobic. Instead of wanting to compete with Britain at sea, he's Pan-Germanist and slavophobe, who wants land for Germany.
Japan is at odds with Russia in the Far East - and Japan is a British ally.