So WI Ricardo dies not die of pnemonia and manages to get reinforcements from Charles.
This one requires Godoy to not act like an ass for once and make something that actually makes sense. I'm afraid we've just gotten into ASB territory.
/kidding.
So yeah, Ricardos gets his supplies and reinforcements when he first requests them, rather than having to halt movements and travel to Madrid to beg for them when he's nearly 70 dieing as a result. So the Spanish continue on the advance, take Perpignan and with it what remains of the French Roussillon.
That's doable.
But now what? France has won at Toulon, the Vendee and the Netherlands. What prevents France from simply moving her massive armies south and turning the tables? I doubt they'll be in the mood to concede victory after taking one single hit.