Why not give the island to Savoy? I know that genoa has quite the fear of them, but maybe if there was enough pressure from France and Britain and the republic was desperate enough, a deal could be hammered out to cede sovereignty.
I suppose the question would be "why." The Corsicans wouldn't be interested in that; they've been effectively their own country for years. The Genoese would hate the idea - they'd probably rather see Paoli win than cede Corsica to Sardinia. As for the British, a Savoyard Corsica is only marginally better than a French Corsica. Sardinia is not a British ally, and the government will still be seen to have betrayed Paoli, who was a very popular figure in England. All it really does is embarrass France, and I'm not sure the King of Sardinia is going to rush at the chance to help Britain humiliate its gigantic and powerful neighbor.
The best time for a Savoyard Corsica is about 20 years before at the end of the War of Austrian Succession, which saw both an Anglo-Sardinian backed expatriate invasion (Domenico Rivarola's expedition) and, near the end of the war, the landing of Sardinian regulars on Corsica. If the WoAS goes worse for the French, giving the Pragmatic Allies more power at the bargaining table, a Sardinian annexation of Corsica is quite possible.