I guess he's fighting to prevent you from doing that. But, honestly, while it would make some sense for the UR to support someone like Austria or France in that endeavor, it doesn't make sense to fight that war by itself. If you want to stop the Germans from uniting, you're gonna have to put some boots on the ground, and that is something you just can't do. Neither can the Ottomans, honestly, since you're gonna have to put pressure on the Prussian homeland to win the war and there is no way Ottoman forces are coming anywhere near Prussia.