What happens if someone fakes a signature to their consent, unless another new way of doing consenting comes about as proof.
It will 100% be abused.
That's not how it would work

Sorry to hear about your Mum OP. MPs have been debating it again recently (https://committees.parliament.uk/co... the,be learnt from international experiences.) but every time it's been voted on in Parliament it gets denied.
My own view is that it should definitely be available, I wouldn't want to have something that leads to me being unable to care for myself like dementia.