I saw and read that thread but I don't want to go down that route. So lets say Anne de Bretagne outlives Louis XII and a French match never becomes possible.
Fair enough. Mary marrying Karl V might actually make things more difficult for Henry, not less. For instance, no English alliance with France is really going to be taken seriously by the French (IMHO). Or if England
does ally with France, it could lead to a rupture between Henry and Mary - as his relationship with Ms Boleyn did OTL. As to the King's Great Matter, Mary was against it from the get-go (and ironically enough, Henry would've been against a divorce under usual circumstances, since if we look at how he reacted to his sister, Margaret, begging an annulment of her marriage to Douglas), and added to that, she disliked Anne Boleyn, who she knew from her time in France. Now, here, she has minimal contact with Anne, but she's likely to still being opposed to it (the matter) on various grounds. Karl V, OTOH, might actually agree with Henry that CoA is past her prime, because, unlike OTL, he has another in at the English court - namely Mary (OTL CoA was his only source on the ground). From what Hester Chapman writes of Mary and Henry their relationship was much closer that Henry and Margaret's. Whether this was simply due to proximity (either in locale or in age) or other factors, IDK.
Also, Karl is likely to start having kids earlier here (strike that, he
will have kids earlier). So, it would be likely (in my mind) that if Princess Mary escapes England to say (the Netherlands), Karl marries her off post-haste to his eldest son. In fact, Karl might even encourage CoA to send Mary to him (if he doesn't approve of the divorce proceedings) in a way he didn't OTL. Or if the pope agitates enough, we might see Karl's son and Mary acknowledged as the "rightful king and queen of England", although this would be the same as the king of France proclaiming Mary, Queen of Scots' as "queen of England" when Mary Tudor died OTL.
*Most of this is probably a stretch, but I sorta just wrote what popped into my head.