I think Britain would have kept the war up until they got the same conclusion as what happened IRL. They weren't about to let France to have a personal union over Spain, it would have thrown off the balance of power in Europe and in the world. The longer the war went the more sour things would have turned out for France, the only high point is that things turned sour for the Habsburgs as well
Hmmm, I think you're right about England continuing to fight, but I'm not sure about the war's end. If, say, after a win at Blenheim (and then Vienna), France makes a separate peace with Austria and knocks it out of the war, then things look dicey for the Alliance.
Without Austria there to help matters, France will definitely eat Savoy, and it may end up eating the Spanish Netherlands as well (though Bavaria had designs on this). They may even make inroads into the HRE. Whether they maintain the conquests, or use them as bargaining chips to get Philip on the Spanish throne is different, though.
I think a possible alternative treaty could go something like this, if we accept that the Two Crowns Party and Grand Alliance stalemate and France fails in its main war aim of setting up a Spain that would eventually be inherited to France.
----------------------------------------------------
(1704-05) Austria leaves war. Charles III relinquishes claim to Spain. Vienna falls and Austria is forced to negotiate with Francis II of Hungary, who in ATL got to meet up with his Franco-Bavarian co-belligerents. Presumably Bavaria gets something. France may extract minor concessions elsewhere.
---------------------------------------------------
End of War:
Philip gives up claim to France when he takes over Spain (as an aside, perhaps the chain of royal deaths are butterflied away).
France extracts significant territorial concessions from Savoy-Piedmont, which is completely occupied by France at the war's end and is in no position to bargain. Direct annexation is unlikely, but possible.
France regains Lorraine and incorporates it into France.
Spanish Netherlands go to Maximilian of Bavaria (he had designs on them and had governed them in the past), or are partitioned.
Sardinia, Sicily, and Naples are anyone's guess. With the Hapsburgs out of contention, France (through the Grand Dauphin) has a claim to them, though England wouldn't want France to have them all. I think we might see France get Sicily, maybe Sardinia or Naples, but aside from that it's doubtful.
England (Great Britain now, I guess) receives significant colonial gains, mostly from France. Basically OTL.
England, as in OTL, obtains Gibraltar and Minorca, and maybe some other minor stuff.
-----------------------------------------------
I dunno, it would make for an interesting timeline, at the least.
France is stronger, though not craycray.
Austria is significantly weaker with Hungary going independent, though that independence may be short-lived.
Bavaria is much stronger than in OTL, and could become a big player in later German Unification.
Speaking of unification, France now assumes the role of OTL Austria as a de facto antagonist to the cause of Italian Unification.