I don't think that would have been possible. By the end of the war Germany was in revolution and the military was in mutiny. The country was in no mood to continue Hohenzollern rule.
In the Austrian Empire the slavic regions were insisting on independence. Although the situation was not a turbulent, the German Austrian republicans would not stand for a continuation of the monarchy.
Although it is true that the Allied representatives, and Woodrow Wilson in particular, demanded sweeping away the old monarchies, internal dynamics were dictating the same result.
The German National People’s Party (DVNP) had a monarchist platform and had a large early-mid Weimar base. I believe Hindenberg was a monarchist.
Politics seems to takes on a life of its own sometimes.
Still hard for me to take watching the western Allies not moving an inch and allowing the communists to surround Berlin and the country around Berlin as a result of what I consider to be convouted politics and Stalin out-negotiating FDR.
I grew up across the street from a Hohenzollern family in California . They changed their name to Zoller.
At the end of World War 1, nobody in Germany wanted Wilhelm or the Crown Prince, who was apparently as much of an ass as his dad. You would have had to go down the line of succession to find a good figurehead monarch.
In Austria-Hungary, the empire had only been held together by personal loyalty to Franz Josef II by his subject. He was himself an institution. When he died, the Empire died with him.
Yes, had the royal institutions remained, Hitler would not have risen. But that scenario violates Henkster’s Law.