Nice challenge. Here's my attempt.
The PoD is during the Franco-German war, leading to Germany annexing all of Lorraine and puppetizing Luxembourg. By this point, Germany can completely dismantle France, which is why Great Britain decideds not to intervene.
Things get intense in terms of an alternate historians excitement when Russia offers to partition the Balkans with AH, as per OTL. However, this time, an agreement is come to, but just like the Anglo-German plans to partition Portugal's colonies, the plan doesn't immediately go into fruition. When Serbia and Montenegro go to war with the Ottomans, Russia begins to mobilizing, urging AH to do the same. Germany and Great Britain try to mediate and get AH not to declare war, at the support on Andrassy, but fails to get Russia to back down. Russia is very successful in the opening moves... so much so the Great Britain declares war, which leads to a second mediation held in Denmark. The Treaty of Copenhagen, the Balkans are redrawn. Russia gains Romania as a Grand Principality/Duchy, yet agrees to leave Bulgaria as a sovereign state.
This leads to a severe changing in Europe's political situation. Great Britain and AH and France form an alliance while Germany and Italy form an alliance with Russia, Greece, Serbia, and Montenegro. Japan enters the mix in the 80s by forming an alliance with Great Britain. The same decade, the Ottomans form an alliance with AH in return for AH annexing Bosnia-Herzegovina. This sets off a diplomatic dipute, but gets resolves. Imagine on par with the Agadir Crisis.
Things finally get hot in the 90s when Russia and Bulgaria go to war for whatever reason.
The US gets involves, but on what side? It's a mystery!
Want a map of the Balkans?
