At the risk of stating the obvious, any licensing system is only an extremely crude way of comparing people and their abilities.
In the UK test flying world we have (so far) operated on a approved basis where organisations, civil or military, applied for approval to the relevant authority, D Flying or the CAA, for J Bloggs to be allowed to do X..
Because the UK test flying scene is fairly small most potential practitioners are known to somebody in the relevant authority so their approval (or rejection) was pretty soundly based on personal experience of the J Bloggs concerned and the job he was going to do.
I suspect Europe will sooner or later require us to go the test flying licence route for all sorts of reasons. But none of those are connected with making sure the best guy gets to do the job
Surely the licence as an indication of a pilots ability is very limited even in the airline business. If you run an airline are you going to employ any pilot who happens to have the necessary licence? Not if you want to use your aeroplanes week in week out I would submit.
I read a letter the other day from a new PPL who said that now he had a licence he did not see why any club from whom he wanted to rent an aeroplane should expect him to fly with an instructor first before he took his long lists of mates up for a fly - after all Mr Avis did not do that before he drove out of the parking lot.
Such is the magnitude of the problem.