What happens if the Allies decisively won against the Bourbon-Spanish forces in 1710 at the Battle of Villaviciosa?
http://en.wikipedia.org/wiki/Battle_of_Villaviciosa
If you want to knock the Bourbons out in one blow, perhaps the best chance is here:
http://en.wikipedia.org/wiki/Battle_of_Almenar
"Villadarias opened the battle with a cavalry attack which was initially successful, but the initiative was wasted by pursuing groups of fleeing enemies.
Then the British infantry attacked the left wing which fled, taking the second line with it. Then the Austrians attacked and destroyed the right wing, where Philip V risked his life fighting and was almost captured by the allies."
An alternate history program from Catalunya Ràdio dealt with this particular scenario on one of its episodes some years back.
http://www.catradio.cat/audio/79292/I-si-Felip-cinquè-hagués-mort-a-la-batalla-dAlmenar
Unfortunately: it is both audio, in Catalan and I don't think we're many here that speak it.
My take is that it would complicate matters somewhat for the Bourbons. Louis, Philip's son, is 3. Not the best candidate one can put to the throne.
His uncles, either Louis the Petit Dauphin or the Duke of Berry, are more suitable and available as well. In the case of Louis, it would probably butterfly the measles that killed him, his wife and his son Louis.
OTL's Louis XV might not have become king in this scenario.