Any time after 1900, have Germany's monarchy fall and replaced with the Weimar Republic or a substantially similar government, and remain a stable Republic until today, and maintain its 1914 territory. It can sue for peace during WW1 or anything else, but cannot be the cause of a future world war if such happens. It can lose Alsace-Lorraine but must regain it without being the initial aggressor, and can lose the OTL portion of Schleswig-Holstein, but not any eastern territory and not Eupen-Malmedy. It can gain Austria, South Tirol, and the Sudeten territory if you wish. By 2012 it should be at least as politically free and roughly as tolerant as OTL Germany.