There were some discussions about WI Joseph Ferdinand of Bavaria had survived to become king of Spain, avoiding the Spanish Succession War. But he was the fruit of as much Habsburg inbreeding as Charles II, maybe even more. So, WI he lives, but becomes a second Charles II, living for more or less 40 years but being unable to produce a heir. How would be a Spanish Sucession crisis delayed for 30 or 40 years (let's imagine he dies around 1737)?