He somehow needs to retrieve some of the lost monarchial powers. The monarchy needs to have enough power to restrain Parliament when it losses its mind and goes into democratic excess. Like its doing now!
Their current system is a case study in why unbridled democracy can be just as oppressive (maybe worse!) then autocracy.
I can’t see how it will happen.
The Monarch used to check the Parliament.
And within the Parliament, the House of Lords used to check the House of Commons.
So their system worked much better 100 or 200 years ago.
The British Parliament has the power to abolish the monarchy. Here today, gone tomorrow. That (among other things) will probably keep William quiet and timid once he takes the throne.
But the monarch has the bully pulpit. And he is the commander-in-chief.
So when is enough, enough? At some point the monarch will have to roll the dice - that or his country is gone forever.