Well, I can advance (spoiler alert!), because I stated it in the pre-TL thread, that Bismarck will not stay as chancelor once the Empire is formed. This means that the German foreign policy would be quite different from that point onwards...
Well, Bismarck was quite successful in projecting the German Empire in OTL as a satiated power to other great powers. Will his successor be as adept as projecting that image?
And what will happen when Russia clash with the Ottomans? If I were Germany, I'll support Greater Bulgaria, the Treaty of San Stefano, and even support Russia gaining Constantinople!
In other words, Germany should hitch itself to Russia. With Russia in the German orbit, France would not dare to even think about revenge on Germany.