What if we go back to the war before the 7 Years War and make for lopsided victory by the French-led coalition in the War of Austrian Succession.
Austria gets crushed (or exiled to Hungary basically) while its lands in the HRE are conquered by France (Austrian Netherlands), and its allies Prussia (Silesia), Saxony (Bohemia), Bavaria (Austria) and Savoy (Milan). The Prussians also conquer and annex Hanover postwar, to bring continuity between eastern and western holdings and counter British support for the Austrians.