Marriages for the children of Queen Anne

So to confirm, we've got

Mary marrying Karl of Austria

Anne Sophia marrying Carl XII of Sweden though might well go unconsumated.

James marrying Ulrika of Sweden

William marrying Marie Amalie thus cementing better relations with the netherlands
 
Kellan, actual claims only by marriage worked for a lot people trough the ages.

Oh, and I am not sure if my 8 corners are entirely correct.
 
So, a query regarding the War of the Spanish Succession, how much would England/ Britain put into the effort if Mary is married to Karl? Could we see Karl on the throne
 
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