Okay, here's my idea:
The British should put a time limit on the Monarchy.
Not like declaring a republic tomorrow, but deciding on a date in the future that ends the British Monarchy.
And there's a perfect date for it coming up!
October 14th, 2066.
A thousand years since the Battle of Hastings. A thousand years of this one specific bloodline ruling England.
Call time on the Monarchy after exactly one thousand years. Nice, and neat.
Even better: Charles isn't living 44 years. He'll be gone in about twenty. Now William? He's what, 40? Yeah, he can live another 44 years. His great grandmother was over a hundred, his granny was 96, William can make it to 84 barring accident or assassination.
So on October 14th 2066, William the Last steps down a thousand years after William the First won the crown.
Nice, neat, and fair. William gets the crown he's been waiting forty years for already, but ten-year-old George grows up without expectation of it.
Have a nice big abdication ceremony, even.
Plus, what an absolute baller move to announce your regnal name as William the Last.
the Final Bill
This is actually a really good idea, I think.