If you wanna play with German unification, maybe have it more focused on the Rhineland? It was a hotbed of republicanism iirc
First off, I think that the Colossus logo looks awesome! Though I'm not sure about the "Colossus of Liberty" idea.
Regarding Prussia, I was thinking that they were trying to do the OTL "blood and iron" unification, but more slowly, due to increased Franco-Austrian meddling. When the revolution came, Prussia was surrounded by enemies, and after large defections to the revolutionary cause, ("Germans shouldn't fight against Germans"), perhaps a compromise is reached, with the figurehead monarchy being Von Hohenzollern, and the capital being in Berlin?
Your description of the causes of the revolution is spot on. And I think that @Bennett is correct that the Rhineland would be the core of revolutionary activity.
As for the Schleswig question, I was thinking that the region would be annexed later on, possibly after the Great European war?
Ok, so I'll leave S-H out for now. I was thinking a Prussian figurehead would work, with kingdoms and principalities maintaining their own figureheads, with theoretical authority in regional legislatures, and smaller states as well as the Rhineland (separate from Prussia to curb Prussian dominance) having no regional monarchs. Basically: Prussia (Brandenburg, Silesia, and Prussia proper), Bavaria, Baden, Wurtemburg, Hanover, and Oldenburg and the "federal Hanseatic cities" (Bremen and Hamburg) are special areas, while the rest (around 1/3 of Germany) is regular provinces. Provinces are represented in the diet in proportion to population, while the kingdoms get slightly more seats than they'd get from population. I see Bavaria, Wurtemburg (very populated), and the Rhineland having much more influence TTL.
I'll be sure to have the kickoff of the revolution in the Rhineland. I see Prussia forming a shaky alliance with the revolutionaries around the early-mid part of the war to fight a common enemy, likely trying to hijack the revolution, and then being forced to compromise later as revolutionaries would probably do a lot of the work themselves and not feel like they owe Prussia everything.
What do you think?