You mentioned three surviving children of James, so James of Cambridge is not dead in the plague epidemics here (and will become first 2nd Duke of York in many generations)?
Good start.
How far are you going with this?
Any spoilers for bride for future King? Though via year of birth I can guess - either a French first cousin (OTL Duchess of Savoy) (b.1669), or for the sake of historical recognition Sophia-Charlotte of Hannover(b.1668)? Or somebody out of left field (surviving Madame Royal or some minor Protestant princess)?
Also, will Rupert of the Rhine turn down the invitation to become a Duke of Simmern-Kaiserslautern in 1673 in TTL or will he accept it thus butterflying away Nine-Years War as we know it? In OTL he was encouraged to accept it even with his spouse being morganatic (he was encouraged to marry Peg Hughes, his second official mistress, at some point of their relationship, and Imperial Law allowed a (costly) loophole out of morganatic marriages for lesser principalities which the Duchy of Simmer-Kaiserslautern is).
And there IS a Conde-type relation cadet branch of House of Stuart, descending from this guy - http://en.wikipedia.org/wiki/James_Stewart,_2nd_Earl_of_Moray, direct legitimate descendants of Robert II of Scotland (they interbred with illegitimate descendants of James V at some point thus creating the confusion).
But the Morays are cadet branch in the sense Conde or Soissons were.
Morays got some sort of prominence due to intermarrying with Argylls. Thus in my TL there is a "kid gloves" attitude towards 10th Earl of Argyll -his mother is one of Morays, thus under Scottish succession laws he is a valid Prince of Blood. Though the proper Earl of Moray in this time period was a Jacobite.
http://en.wikipedia.org/wiki/Archibald_Campbell,_9th_Earl_of_Argyll
http://en.wikipedia.org/wiki/Alexander_Stuart,_5th_Earl_of_Moray
And as for marriage for Rupert and Royal Bride - he'll be landless till about 1673 when the secundogeniture title will be promised to him, and unlike Emperors of HRE, Kings of Britain don't have the brides of principal dignity waiting around. So the possible brides during 1660ies is either Lady Frances Bard (plagiarism from my TL) or...
http://nl.wikipedia.org/wiki/Maria_van_Nassau_(1642-1688)
She was betrothed to Rupert's cousin, Louis-Henry of Simmern-Kaiserslautern, but with England doing much better in Second Anglo-Dutch War the betrothal may be broken and she'll marry Rupert as part of peace negotiations. A mirror of OTL marriage of Mary Stuart to William III, if you like.
And she and Rupert MAY have children - it was her husband who had major fertility problems and health problems in general.
Maria of Nassau is more interesting character in regards of possible bride for Rupert as she may play into ATL outcome of Second Anglo-Dutch War and Orangists wanting separate peace (sort of reverse of OTL Mary and William).
And Rupert disliked Charles-Ludwig probably even more than Charles II did, so with no ulcer for Henriette-Anne of Orleans OTL Duchess of Orleans will probably become Princess of Orange or Duchess of Courland as was planned originally. I simply cannot image Rupert playing the matchmaker with the brother he dislikes. Not to mention Anne Hyde didn't die of cancer until 1671, and if Henriette survives, the marriage negotiations may be way ahead with William III or Prince of Courland.
However - IF Rupert is married in 1666-1667 (a "trophy wife" I suggested) his relations with Charles-Ludwig may improve slightly. And he may offer a help in negotiations. But with longer-living first Madame the most plausible outcome for Elisabeth-Charlotte is to end up as Princess of Orange, as I suspect 1671 will be too late for any advances on part of Duke of York.
BTW, from the medical POV the esophagus ulcer aggravated by neurotic anorexia (diagnosis of Henriette-Anna) is quite severe sh*t by standards of 17th century medicine. And I simply don't see how you butterfly a better psychological environment for her. She was simply not created for long-time stresses (same predisposition for neuroses is believed to kill her eldest daughter).
Buying a few extra years of life, though, I can buy.
Philippe took part in the War of Devolution in 1667 while Henrietta remained at Saint Cloud in a state of pregnancy. On the field, Philippe took an active part in the trenches at Tournai and Douay and distinguished himself through his valour and coolness under fire.[54] But Philippe later became bored with battle and interested himself more in the decoration of his tent. Hearing that Henrietta was ill due to a miscarriage, he returned to Saint Cloud, where she was recovering from an ordeal which almost cost her her life.[55] Upon her recovery, Philippe returned to the battlefield and distinguished himself at the Siege of Lille (1667).[56]
Amelia was betrothing all her daughters so she'll try to do that, her daughter being the only capital she may invest in separate peace. Which she wishes as is English being supportive of reversal of Cromwell's ultimatum = William III becoming Stadtholder.
And the first recorded symptoms of "intermittent, intense pain in her side" were recorded in 1667. But I'm quite careful with medical PODs, and Philippe de Valois suffered of epileptic symptoms.
This pregnancy being successful may be a POD you want to look in for Henriette. This is the only thing in her medical history that may help here.