Hell, with Romania and Bulgaria switching sides sooner
This is a big assumption on Romanias part. With no Prince Michael things are likely to be much tougher for the Soviets ITTL. If Romania stays in the fight even a month or two longer it can drastically change the timeline of the Eastern Front as we know it.
Also a Finnish SSR is interesting in its own right, and would allow the WAllies to take over more of Germany.
Why does a Soviet Finland lead to a larger WAllies Germany? I don’t see the connection. Also a Soviet Finland likely leads to a very different history of Cold War diplomacy. Not to frame Finlandization as a good thing, but I’m not sure who is a driving force for something like CSCE without a neutral Finland. So I’d rather they get the OTL treatment if possible.
I don't think we'd see a Germanic Prussia post WWII, I think everyone was okay with the destruction of it. Maybe we'd see a scenario where Kaliningrad is created to 'become the model SSR where everyone lived together in peace and harmony' but a name change and the moving away of a lot of Germans would be inevitable at this point.
I can see a Soviet German Prussia if the Soviets feel penned in with a smaller sphere of influence. In that case more proxy’s are more important than destroying German militarism at its roots. They could even see such a thing as beneficial if they think they can harness it.