Much as we only notice those with a massive chip on their shoulder about not being ex-mil, how much better they are because they worked on the N Sea, and how no-one could learn from ex-mil (arrogant) pilots - because they keep banging on about it on these pages.
Post-PPLH mentoring is a good idea and most of those without egos on here recognise it - it doesn't have to restrict their freedoms or cost a fortune, but it is a good idea and those that want to learn and improve will - those that don't won't but they will probably be in a minority.
It already exists to a large extent in flying clubs. In fact in my other life as a glider pilot whereby no licence is currently required to fly IFR or cross country, gliding clubs and the BGA system is supervision and mentoring par excellence. Which is great.
So my point is not that mentoring is ineffective, it is that it is unfeasible to enforce it for PPLs. The whole point of having a licence is that you can operate independently! Of course it is the usual story of those who don't really need to will seek advice and good counsel anyway, those who really do need it are too arrogant to realise and so won't.
So far folk seem to have decided that in order to avoid a pilot flopping his R44 into a field we must eliminate young instructors - even though we have no idea who this chap's instructor(s) was/were. And that he is an arrogant fool who wouldn't have crashed if only he had been forced to have some mentoring.
In these days of evidence-based regulatory actions, that is nothing short of barking.