The German Confederation in OTL called a Congress of Princes for 1863 or 1864 I do not remember exactly. It was to reform the German Confederation. In OTL, Bismarck had Prussia boycott the conference thus removing a vital player astride northern Germany and undermining the gathering’s potential for legitimacy.
If Prussia participated in a non-obstructionist manner (perhaps Bismarck not in power or having been fired), what potential reforms to the German Confederation system and Constitution could have occurred.
If the result were a more empowered Confederation, how would it’s constitution be different from OTL’s federal constitution for the Prussian-led 2nd Reich of OTL?