and the CAA's oversight role easier...
How much easier do you want it to be?
They might improve things by say, simply coming up with a number of hours flown, in a number of days, on a type. To establish what that number should be, they could ask an organisation with experience in such matters, like CFS. Then they could state that a DA is only valid when those preconditions are met.
I don't think that with current e-filing systems, it is too much to ask for ALL pilots to be asked to "validate" their licences by logging on once a year and entering some figures.
How much it would do for safety, I can't say. But it would be a start.