Can I just say I love your icon?!

There'd be still a lot of factors against it - the Versailles Treaty, the Great Depression, the whole authoritarian mindset had been internalized since 1870 at the latest and wouldn't have suddenly gone away

Oh, most definitely! The road to democracy would still have been hard (personally, I always think that is still an aftershock of the ultimate failure of 1848 and how it failed. Oh, and yes, ridiculous is the perfect desriptor for Hitler's prison sentence. As for Hindenburg and the Monarchists: I wonder if in this hypothetical alt!Germany, it might have made sense to nominate Stresemann? IIRC, he used to be a monarchist and skeptical of the republic in the first few years as well, so he might have won the skeptics over.