In 1714, George I ascended the British Throne.
Let's say he falls off quickly.
Let's say instead of France, Austria sponsors the Pretender. Remember, they weren't allied with the British at this time.
In 1715, dragoons sent to arrest Jacobite leaders in Oxford, Bristol, Plymouth and more instead defect due to a conspiracy. John Churchill, 1st Duke of Marlborough throws his weight in favor of James Francis Edward Stewart. 35,000 Troops descend on London.
The Whigs scramble some militia which are defeated, but buy some time for more Hannover-supporting army units to come stop Marlborough.
George I agrees to discuss things with Marlborough. He then signs an agreement to abdicate the throne in favor of James Francis Edward Stewart in exchange for several conditions. George I's family gets a claim after James Francis Edward Stewart's decedents should the new king die childless. GB will give George I and his descendants a pension scaled by GB's spending. They spend 3000 pounds on anything, and 1 pound goes to George I. This pension will continue after his death to his hiers and it will stop when his great grandchild through the senior most line (oldest son of oldest son of oldest son...) dies (so basically a multi generation pension). Marlborough accepts, but he wasn't actually given authority by James Francis Edward Steward to do so.
George I leaves the throne, never realizing Austria was plotting against him, just knowing the Pretenders lived in (make up some place of your choosing) before coming to Britain.
James Francis Edward Stewart is crowned James III.
Well... what effects would this have? Would there be a counter conspiracy? Would GB accept Pragmatic Sanction without question (in OTL, they forced the Ostend company to disband to accept it?) Would GB be stable? What about poor Hannover, losing its opportunity to get the British crown?