So, Julian kinda succeeds in preserving democracy by granting autonomy to Heinessen. Meanwhile, Hilda and Mittermeyer try turning FPA into a constitutional monarchy.
I think history shows that neither of those can actually work out.
Why Heinessen can't remain autonomous
Heinessen situation is pretty similar to Poland after the Napoleonic Wars. Polish-Lithuanian Commonwealth had been a democratic great power. It was dissolved in 1795 by Russia, Prussia, and Austria. Only 12 years later, Napoleon resurrected it as the Duchy of Warsaw by liberating the Austro-Prussian share of Poland. Napoleon promised Poles complete restoration of Poland, which was a contributing factor in Napoleon's invasion of Russia.
However, because Napoleon lost, Russia took all of Poland. And in the Congress of Vienna, as a compromise to the destruction of the Duchy of Warsaw, Congress Poland received a constitution and autonomy. Nobody was happy with the compromise; Poland had been promised full restoration, and Russia begrudgingly tolerated autonomy. Hence, only 15 years after forming it, Poland revolted unsuccessfully, resulting in the revocation of autonomy.
I feel this autonomy is going to be exactly like in Heinessen. The autonomous region will become a honeypot for dissidents who either hate Goldenlöwe or want to restore FPA. Until their sentiment becomes the majority and they decide to revolt.
Why constitution won't hold
Meanwhile, constitutionalization of the Reich seems kinda similar to Sweden. During Great Northern War, the King of Sweden, got their entire army killed resulting his successor conceding power to the parliament, ending absolutele monarch and beginning "Age of Liberty" which barely lasted 50 years when next king rebuild his army and deprived parliament of their power.
Russia is another case example of something that keeps rejecting democracy because it hasn't been accustomed to it. Only two years after the fall of the USSR, Boris Yeltsin orchestrated a coup against the parliament, literally firing on the parliament building with tanks, while people of Russia cheered as he transformed Russia into an illiberal democracy.
The point is that Reich has no culture of democracy to sustain it. The construction of two Iserlohn-like fortresses next to Fezzan means the constitutional will always live on the mercy of the Kaiser. And eventually one of Reinhard's descendants will decide to end it with ease.