First of all I would like to say that although I love a Dutchwank, I am glad this never happened. I do not like the idea that my country would be involved in pretty nasty warcrimes (expulsion of the Germans of new Dutch territories) at the end of world war II.
Secondly, although we Dutch do pretend to dislike the Germans, we actually don't. The Germans are pretty decent people and very important to the Dutch economy. We just like to pretend we dislike the Germans in a big brother-litle brother way (not unlike how the Flemish hate the Dutch or the English hate the Americans, all in a friendly way).
Anyway the way for the Dutch to gain more anexations after WWII (they did gain some small parts, but all were returned in the 1960's), would need different postwar relations betwen the western allies and the Soviets. After the war the allies wanted a strong Germany as a counterbalance against the Soviets. So if the Soviets weren't considered adager, I could see various annexation of German territories by various western nations (including fr example a French Sarland). Another way could be a more succesful Soviet Union. If they managed to capture all of Germany, I think they would want to limit influence of this new Communist Germany, trying to avoid that Germany would be the major nation in the communist block instead of the Soviet Union. So they could try to split up Germany and give various German territories to neighbouring nations, including a communist or Finlandised Netherlands.