CCTV would have all sorts of privacy issues with patients, it's a difficult solution. It you wanted to use it in case of malpractice where the negative effects weren't known for years, you'd end up having to keep the footage (and all of it) for years. Technology is probably the answer where the drugs administered (and by who) is automatically recorded. If you can track an item being stolen from a supermarket, you can track a medicine being given to a patient in a hospital.
As for two medical personnel that isn't going to happen. I did have some stats around that. I witnessed on a couple of occasions last year, an emergency alarm being rang by a nurse on a ward because there weren't enough nurses on shift... in a high dependency unit.
But Whistle-blowers yes. All our institutions have a major issue with that full stop.
One of the problems was that Letby also used innocuous non-drugs. Plus I know this through other circumstances, the correct volume of drugs can be removed from the cabinet/trolly, then either illicitly withheld or played with so that one patient gets more, one less.