I would remind everyone that Saxony and Bavaria openly and opportunistically allied with Napoleon. Prussia could easily do the same if they stay out of the initial coalition wars, ideology be damned, especially given their traditional friendship with France and relatively liberal outlook; Prussia, prior to Vienna, was firmly focused on the Baltic, with only peripheral territories in the Rhineland. If they could trade Julich-Kleve for some combination of say Saxony, the OTL Polish territories, and a Hohenzollern king of Livonia/Lithuania alongside the alliance they'd go for it, not least since Prussia never really wanted the Rhineland to begin with (distant from their powerbase and full of irascible Catholics...) and only got it because Britain and Austria insisted on having a power to contain French ambitions against the Rhineland.