Any way the South German states could remain in Austrian sphere after the Austrian-Prussian war with some kind of Prussian victory
I have a very solid theory, but to give away the details would be a spolier for my timeline (shill alert). One thing I will say, though, is your best bets will likely involve the War drawing in forgein mediation of the peace. If we're going with the fronts panning out exactly as they did in our timeline, the most obvious way to do this would be for the negotiations as Prague to have Prussia going with King Whilhelm's desires and pushing for the annexation of parts of Bohemia. This likely sets off Balance of Power alarm bells in London, Paris, and St. Petersburg as Austria agreeing to such terms combined with the shouts for greater autonomy coming out of Hungary raises the Spectre of a now highly exposed Vienna being effectively knocked out of Great Power status. In that case, expect to see the 1877 mediation over the Sick Man of Europe to take place a decade earlier with a different Sick Man.