Have King Ludwig II of Bavaria declared mad or resign in 1864 or 1865 and his brother Otto declared incompetent about the same time. Their uncle comes to the throne then instead of 1886, if he can link up with the Hanoverians in the Austro-Prussian War it changes the course of the conflict and hands Prussia a notable defeat in the field early on. Bismarck will want to get out before France (eyeing Luxembourg) and Russia (eyeing non-congress Poland) get in. Prussia is at best contained, at worst isolated, and perhaps contained to OTL Eastern Germany minus Saxony. Though the Silesian lands are enough for her to industrialize, the remainder of Germany becomes a pro-Austrian confederacy or perhaps even part of the Empire itself over time. Bismarck still had influence and maybe gets a second chance later on, but in this case he faces a French Empire still under Napoleon III, and Austria firmly in command of both Venice (possibly taking Milan back if the Italians fare poorly) and much of Germany, and a Russia that might want to make Prussia its satellite if not an outright conquest. Perhaps the Oder becomes a dividing line for Austrian Germany and Russian Prussia?