As many have wrote, there are a number of hypothesis on how the French (the Spanish were not at Saintes) could "win" the battle.
0. OTL, de Grasse asked to be removed from command in October 1781. Vaudreuil would be in command in 1782, but this would also butterfly away "the" Saintes
1. On April 9, de Grasse and Hood sparred a row of distant cannonfire. A first PoD could be a pursuit of Hood's squadron (12 ships) by de Grasse's fleet (31 ships)
1.a. Hood is defeated, maybe captured or even killed (with far more extensive consequences, as Hood was Nelson's mentor)
1.b. Hood's squadron have to disengage and flee and cannot regroup with Rodney's main fleet
2. On April 10, FS Zélé is not accidented and need no towing. When Rodney (37 ships) appears on April 12, de Grasse can refuse the fight and try to regroup with the Spanish (as ordered by the Ministry)
3. During the OTL fight, the signals are better understood.
3.a. Bougainville's squadron slows down in order to keep the line intact.
3.b. When the center of the french line is trapped, Bougainville turns back to save it.
Any way, if the battle is a bloodless draw, a bloody draw or a victory, it is still positive for the French, as they can expect the Spanish squadron (12 ships) while the British cannot reinforce the West India Station with so many ships on a short notice. The French had had some success in islands invasions (Saint Kitts in February), so a successful landing in Jamaica is possible.