To bad a majority of people in the Lance Empire are brainwashed into doing what the Emperor wants, and it has always been a dream of the Lance Empire to unite all Germanics under one banner. Numburg Loyalist might be a problem, but nothing that can't be put down. The Slavics in the east also might cause trouble, but the Germans outnumber then and a majority of the army is German.

Oh and part of the switch was that the UGF would agree to uphold all treaties the Lance Empire and Numburg had made. You still get your stuff Illuvatar.