Oldenberg was a member of the Confederation of the Rhine and was annexed by France in 1810. It was the only member of the Confederation that was annexed by France after the Confederation was founded in 1801.
Hanover, Brunswick, and Hesse-Cassel were not members of the Confederation of the Rhine. They were later grouped together as Westphalia. The Hanseatic cities, including Hamburg, were not members of the Confederation either. They were directly annexed by France.
So the idea that Napoleon would have dismembered the Confederation states is not quite accurate. And some of them, such as Bavaria and Wurttemberg were actually given territory by Napoleon.
I would highly recommend, among other references, The Struggle for Mastery in Germany, 1779-1850 by Brendan Simms.
The 'viewpoint' that Napoleon routinely dismembered German states of the Confederation isn't an accurate one.