I would say it is utterly impossible at this point without permanent occupation of Britain by a French army.
By 1750 or so I think Great Britain was like 99% Protestant and violently anti-Catholic protestants at that. A Catholic Stuart dynasty would be a non-starter. If the House of Hanover died out from some plague or did something utterly repellent to Parliament (George I through IV never did anything close to getting thrown off the throne), then Parliament would just do what they did with William and Mary: pick the Protestant they liked best and put them on the throne regardless of how close they were in the legal succession.
If the House of Stuart somehow went Protestant during their days in exile...the odds would still be staggeringly long.
Sorry, only a French/Spanish army occupying Britain would put the House of Stuart back on the throne.
Ireland would be a possibility and some of my TL's had a successful Irish Rebellion with French assistance and the Irish calling back the Old or Young Pretender or one of their heirs from the Royal Family of Savoy (1806 timeframe after the legitimate direct male succession of the House of Stuart came to an end).