But there is still the issue of motivation. English princesses post-Glorious Revolution weren't generally marrying French princes anyway. I'm not sure why they would change that to get a marriage with a deposed exile; it's not like the Bourbons have any leverage at that point. And remember that the Royal Marriage Act is in effect, so they have to get an ok from the King or Parliament.
So why would a British prince/princess trade even a remote chance at succession for a marriage to a homeless exile?
I meant it could be a condition for aid. Marriage alliances were still alive and well so it could be a requirement for British aid. Lets get away from the marriage for a little while and focus on the bigger picture. How would Louis XIV and his family's survival affect France and the revolution? Would there be more or less intervention by the Great powers? Would an early intervention be successful? Or would the only difference be which Bourbon is restored at the end of the war? Though I wonder if a Louis XVII would be able to prevent the July Revolution? Or would he be just as reactionary as Charles X?