They had already Federalized the Belgium Kingdom under there Military Command
Giving the Flemish right to self-government, (something the ruling Walloon elite always opposed)
Territorial changes, everything east of river meuse would become part of Prussia kingdom, means allot of Towns like Liege, Huy and Namur become divided.
The local Walloons had two choice: leave there homes and move to Walloon, or stay and learn German
German Military presence in Belgium, according some documents, the Germans Army wanted to take over several Fortresses in Belgium and use them.
Next to that the Harbor of Antwerp would be enlarged for German Navy and mercantile marine demands.