Alongside the surviving William, Duke of Gloucester timeline thing I've got going, I'm also considering a scenario where Charles, Duke of Cambridge son of James II and Mary of Modena survives into adulthood and his father remains King of the three Kingdoms. Consequently, I'm looking for potential brides for the lad, and am of the opinion that James would look to marry him to a Catholic, whose family is allied with France.
Possible options include:
Elisabeth Charlotte of Orleans, daughter of the Duke of Orleans and niece of Louis XIV, born 1676, otl she married the Duke of Lorraine.
Leopoldine Eleonora of Neuberg, whose sister married Peter II of Portugal b 1679.
Sophie Hedvig of Denmark, daughter of Frederick IV of Denmark b 1677. Not necessairily on the cards, but possible, she is protestant, which would help.
Hedwig Sophia of Sweden b 1681, daughter of Charles XI of Sweden, who I believe was allied to France.
These are the four main candidates I've found, if there's anyone else please do add them to the list, as well as who you think is the most likely.