I usually have little time to create things, but more to think about stuff, so I think you could add a few nations to your mod.
One:
https://en.wikipedia.org/wiki/Transnistria_Governorate it was a puppet of Romania, which could be integrated later, or it could gain its freedom if the "stars align" with events.
Trubchevsk Governorate. Now this is a bit tricky. Only a handful of books mentions this. A certain Melnikov who was the former police chief of Trubchevsk created a kind of free state.
The have beaten back every single partisan attack and restarted the work in factories and the fields. It actually worked.
The got later reinforced by a German cavalry unit called Reiterverband Trubchewsk led by a certain von Winning.
Just to show a single battle, in june 15 1942 more than a thousand partisans have invaded the territory, but they were beaten back bloodied. The only German support was the cavalry unit.
The Trubchevsk militia became veterans and skilled. Later on they were shipped to France and they surrendered in Normandy.
Trubchevsk could found a separate Russian ideology. They could integrate either Bryansk, or a greater part of Chernigov. I think the Germans would pretty much support a working and stable territory amidst chaos. (Less partisans and more working factories are always useful for them.)
They did not found any far right parties and such, even planted some red banners on the factories, but they were not communists.
Maybe they could became a moderate left-socialist nation who could eat up former Soviet territories fast. (A socialist and friendly nation would be popular.)
Lepel Republic:
Otl Kaminski was beaten out of Lokot and created the even more short-lived Lepel Republic. In this Atl he would be pitted against Voskoboinik and his nationalistic irredentist Lokot Republic.
He would certainly try to coup it and if he fails, than he would move out with his warbands and created the Lepel Republic. It would probably declare war on the White Russian nation. (And they would have a chance, since so many renegades and scum were circulating in that region, that he would have a horde in no time.)
It would probably happen after the death of Hitler.
https://en.wikipedia.org/wiki/Italian_governorate_of_Montenegro (I don't quite remember if it was in the mod)
In case Hitler dies, some nations could pop-up (so smaller nations would do something and not just sit out everything):
https://en.wikipedia.org/wiki/Kolky_Republic (Rk Ukraine could fall in to a civil war with multiple nations)
https://en.wikipedia.org/wiki/Bihać_Republic
https://en.wikipedia.org/wiki/Republic_of_Alba_(1944) (Mussolini would be popular, but a general socialist uprising could stir up trouble even for them)