Glad to see that I'm not the only one interested in discussing the War of Spanish succession (shameless plug for thread I started last night)
Anyway, what you are (mostly) describing is the situation that had occured in OTL by 1720 by the Treaty of the Hague. The House of Savoy was forced to trade Sicily for Sadinia by its erstwhile Allies, in no small part because Victor Amadeus II was viewed as a snake by all involved.
I am not sure what effect giving Sicily to Austria seven years earlier would have. The Hapsbourgs lost the two sicilies to the Spanish Bourbons after the War of Polish Succession, and I don't think another seven years to rule over Sicily would really change that.
Savoy might be in better shape if they didn't waste their resources trying to establish their rule over Sicily, and instead could have immediately turned their attention to integrating Sardinia into the Kingdom. Plus, adding the Duchy of Milan would make the Dukes of Savoy a much stronger power in Northern Italy, though the Duchies would not be continguous, inviting conflict with Genoa. Overall I think this new power would make Savoy more likely to be drawn into subsequent Wars between Austria and France, though they might stay out of the war of Polish Sucession (since they entered that war to take Milan, which they failed to hold after the peace). Overall, I think the acension of Savoy from a medium power to a regional power would be a mixed blessing for Savoy, and they would have a very hard time holding onto their newly acquired territory even before the French Revolution.