@Willy VerebReligion was one sticking point for Frederick William III. So I wanted to cover it. Also long term said attempt had far reaching consequences. It can be reasonably said that in this timeline there will be no Kulturkampf, or if it still happens it'd be quite different. I know quite a few things happen but as a non-German I am not as familiar with this period even after weeks of sporadic research so I left it there. It took me half a hour to confirm that Prussians do believe in God-given right to rule (granted, I wanted to make extra sure for some OCD reason).
It's fine for a start, could probably go into more than religion. I know in personal channels me and a few others have talked about some aspects of Prussian society since the end of the wars.
Another problem is that between 1809-1825 the details are a fuzzy mess thanks to Nappy destroying Prussia in this timeline and that there aren't enough details in the OP and the Char section to have me know whatever the hell I can even include. A destroyed Prussia is also a gigantic butterfly effect for, surprise, Prussia so I preferred to gloss over the pre-1825 era.
I did include enough implications about social changes to know more about this Prussia. For example it being mainly protestant and liberal-ish leaning gives it less favor by certain German states so Austria has a bit more of a leeway. OTL, the German Empire united by Prussia was almost set in stone after 1815 and Austria was desperately trying to unfuck their very slim chances (and of course failing). This Prussia, ekhm, Prussia-Saxony is weaker than OTL, has a bit more mixed support and didn't exist when OTL the Frankfurt assembly wanted to crown the Prussian king the emperor of Germans.
I do plan to have other sections than just history in the writeup, hopefully it clarifies things further. For example Prussia didn't get all of Rhine-Westphalia. They have a presence there but mostly their pre-war territories. This will also have an impact on Berlin's development and generally the Prussian industrial power. On the other hand they got all of Saxony but then effectively also lost it (it becoming a separate state under the same king). So yeah, an interesting scenario IMO.