One thing that always surprised me was how reasonable Hitler was during the initial armistice. I would have expected Kaiserreich-levels of annexation, at the very least Wallonian Luxemburg and Nanzig,the west was never Hitler's priority, but I know he had plans for the Netherlands, Belgium it's up to you since he had several ideas (integration, partition, puppet state)
The Reichskommissariats, to me, were always planned as temporary holdovers until the region was sufficiently pacified and ready for annexation or formation into a new puppet state. A chapter on the various governances coild be interesting.
What were some of the plans Hitler had? I only know about the Dutch Nazis pushing for a Greater Netherlands (Dietsland) aligned with Germany or outright annexation.