You need to get rid of Bismarck, at the least, to achieve something like this.
I think the problem is that the only way the German princes are going to bow down to a unified state is through the use of military power. Basically, "people power" was defeated in '48 and clearly couldn't overcome the German states. So Bismarck decided to pursue the only course of action that could bring about German unification, using Prussia's superior military to force the other German states into line.
Without Bismarck's use of force I doubt that any of the other German princes will be able to bring about German unification. The only one who would be able to do it peaceably would be the Austrian Hapsburg Emperor. The problem is that Franz Josef was long-lived, unimaginative, and non-nationalist. If he were to be assassinated and his brother Maximilian become Emperor, then I think Maximilian might be willing to go for German leadership.