I have no doubt that Katherine and William will fight tooth and nail to make sure Harry is never regent with whatever legislation is necessary. If the regent cannot be Katherine I would actually think Edward would be the better choice.I think someone on Reddit may have hit it on the nose when they detailed:
Charles is dying. William will be King. George is under 18. If something happens to William there will be a need for a regent. The regent must be domiciled in the UK.
Catherine can’t be Regent until the UK Parliament changes legislation to allow it. The UK Parliament is a mess right now.
Assume William will make this change when he is King but in the meantime, if Harry couldn’t be Regent, it would fall to Andrew or at least he could claim it which would be the death of the Monarchy.
All that plus giving the kids a chance to know their grandfather before he passes makes sense to me.
All of this is speculation but I can see Charles not wanting to leave any loose ends before he passes.
He is younger than Anne and I suspect William and Kate trust him and Sophie far more than Harry and Meghan. The public too.
An easy law saying king/Queen can pick anyone of Counselor of state to be regent would be done.
