Possibly in the aftermath, the "Republic of German Austria" (a rump state claiming all Austro-Hungarian lands with ethnic German minority survives. It eventually joins with the Weimar Republic. That means no more German interest in the Slavic lands, for now.
I don't know what you mean by "better fit the provinces in Victoria."
Good idea, but could I possibly get away with reshaping Poland a little bit? Here's my idea:
The first president of the State of Slovenes, Croats and Serbs is Marjan Brikin (Again, I need a better name that is still allegory to my name, Morgan Brikiin). He is one of the shapers of the state, and maybe somehow it's called the Yugoslav Union instead of the annoying name which I'd rather put in an acronym, SSCS. Basically it survives longer than it did in OTL, and it doesn't join under the Serbian monarchy.
Somehow the Yugoslav Union might absorb Serbia, Montenegro, and Bulgaria. They become economically booming, and the nation survives through democracy, where each state in the YU (Slovenia, Croatia, Bosnia, Herzegovina, Montenegro, Serbia, Macedonia, Kosovo, and Bulgaria) gets equal say in the government.
Basically Marjan Brikin is like the South Slavic George Washington. He heavily admires American democracy, but he just doesn't like the way the United States has treated the natives of America. He's Slovenian, purely just in case I need to restore the original file in Victoria, which is Slovenska Krv, Serbian, while the current one is Slovenska Kri, Slovenian.