Would it have been successful if Mary, Queen of Scots had married King Henry VIII's son, the future Edward VI?
Henry VIII wanted to push that plan, but Mary's father didn't, that is why their shipped her abroad at the first chance they had. The "Auld alliance" has been very important for Scotland, it was a way to contain England against his obvious attempts to either win, or subjugate, Scotland by iron or marriage. Same they did with Ireland but by iron. Marrying the dauphin to Mary was a way to create a Catholic buffer there, even if most of Mary's subjects were presbyterian.
Also, mind Edward VI was a staunch protestant, a champion of its faith while Mary was of hers. I can't think that bond working but worst things had happened in that island so... who knows really. My main point would be, it was in the cards for Henry but not for Mary's parents.