I find that idea doable with some dose of luck, which Wettins lacked IOTL, I tought about several options:
* Biggest challenge and require a lot of luck for Wettins-Augustus II happened to be military genius and skilled politician, he prepares better for Livonian campaign and takes command personally. Augustus defeats Swedes during crossing of Daugava, taking Charles XII prisoner, at the same time Carl XII happened to be reasonable enough to negotiate peace. Victorious Augustus gets Baltic Duchy for his House, which increase his chances to secure succession of his son, patiently, corrupting right people, he builds support base in PLC, trying to not piss off nobles too much.
* Emperor Charles VI left surviving son, no War of Austrian Succession, so Austria keeps Silesia, or even better:
* War of Austrian Succession still happens, but Austrians with Saxon help are able to regain Silesia, as reward for help, Austria agrees to give Saxons strip of Silesia, to provide Saxony with land connection with PLC, and agrees to support Wettin candidate in next election.
* Empress Elizabeth of Russia is healthlier and lives to old age, Prussia is defeated in SYW, Saxony, allied with Austria and Russia against Prussians, like in previous case gets strip of Silesia. Pro-Austrian Elizabeth could agree for election of next Wettin-perhaps Augustus III lives few years longer (less stress), untill his grandson 18th birthsday? Then after election of Augustus IV, there would be no need for election untill 1827!
In such case Wettin would be good solution for both Austria and Russia-Wettins are Austrian allies, OTOH Augustus III spend his reign in Dresden, rarely even appearing on Polish soil, and made zero effort to make any serious reforms-perfect candidate to keep status quo. Prussians would not be happy about this, but they were defeated in SYW recently and don't have much to say now. If next Wettin gets Polish throne and rule in Augustus III's style (from Dresden), Polish anarchy continue, no Familia's reforms (Familia without Russian support never reach OTL position), which pissed off both conservative nobility and Russia, Wettin on Polish throne became part of estabilished political landscape of Central Europe, after three generations on the throne seen as something natural. Now one thing could push PLC forward-Corsican Devil (OK, Napoleon could be butterflied away with such early POD, but there could be some 'Breton Devil' or 'Gascon Devil' taking his place), despte fact, that ITTL he would be seen by Poles as invader, Anti-Christ, tyrant, trying to destroy Sarmatian values...