Part of me was hoping that Isabel Luisa would have lived longer to be England's queen but I'm guessing that she dies here in childbirth.
Also wouldn't the title Duke of Brittany go to the Dauphin's eldest son?
Given that Catherine of Braganza's death and Charles' remarriage to Margaret Theresa of Spain has utterly changed things. Wouldn't it be more likely for someone like the Duke of Burgundy or his younger brother the Duke of Anjou to be born a girl? If the Grand Dauphin were to have a daughter in place of a son then I can see Charles wanting to marry his younger son to her. Though this means that most, if not all, of his children will be tied to France.
The precedence of the titles in the French royal family is somewhat complicated. The heir apparent and his heir apparent and the latter's heir apparent did not have a separate estate from the crown, so they used titles belonging to the French crown (Dauphin > Burgundy > Brittany). The younger sons had or were expected to have separate estates, so they used titles corresponding to these estates (Orléans, Anjou, Berry for the Bourbons ; Orléans, Angoulême, Anjou and Alençon for the Valois). At the end of the 18th c., Louis XV, afraid of the cursed reputation of the Anjou title, started to use "crown" titles even for the younger sons (Aquitaine for the second son of the Dauphin, Provence for the fourth and Artois for the fifth), but these crown titles were only a front, as the junior princes were given traditional estates (Provence got the duchy of Anjou, Artois got the duchies of Berry and Angoulême). It was also expected the sovereign titles of the princes were not to be inherited by any sons (Artois' sons were Angoulême and Berry, duchies he actually owned).
OTL, Louis XIV had quite a large choice for his grandsons, as the only title already in use was Orléans, so he went for Anjou and Berry. But things could get more complicated ITTL for later generations if Anjou stays in France and if Berry died as he did OTL. Maybe the younger sons of Louis of Burgundy can get Alençon and Angoulême, but for the third son, they would have to go in uncharted territory, either playing it like Louis XV and using "crown titles" or granting titles corresponding to future new estates, such as Touraine or Poitiers.