I suspect that there would be some Jacobites who would even more pedantically insist that he should be Francis III of Scots, on the basis that François II of France was briefly king of Scots after being granted the crown matrimonial in 1558.
I think the idea that even the Stuarts had any interest in Gaelic at all is sort of revisionist, really. James V and VI certainly didn’t. Still, Gaelic was certainly the native language of most of Scotland for a time, and of the Kings of Scots for a few centuries. Pictish, Old Welsh, and Norse > Norn have been stamped out, without leaving enough data to revive them effectively. You could substitute Modern Welsh or Faroese, I suppose, but Gaelic is still around.
Anyway, I suggest we give the Scots Prince Harry for their king, and leave William in line for England Etc. That way we let the thrones diverge but take a calculated risk that they might once again merge.
“Give”? Very generous of you, I’m sure. And what title do you intend to give to your hypothetical King Henry?
Macbeth II (a regnal name).
Let Annestep in as Queen - tell me that wouldn’t chafe Charles’ biscuits. She’d rule w/ an iron, if gloved, fist (the better to hold a crop); she’s even been married in Scotland, plus has staved off a kidnapping attempt on herself and first husband.
“Come w/ me, I’m kidnapping you for 3 million pounds.”, said Ball.
“Not bloody likely!”, said Anne.
“Head punch!”, said passing boxer to kidnapper.
Plus we already know she gets along w/ the English queen, so that’s a nice change from the last time the queens of England and Scotland met.