IO540,
I quite see the point - and it had worried me too in the context of a universal mentoring scheme.
However, it does seem to me that even if a few clubs/schools adopted such a scheme then it would/might have overall benefits to the GA community at large. It also may result in those schools/clubs being seen as in advance of others in the provision of 'aftercare' to their flying graduates!
Really, I had not thought of it as a cost-sharing scheme for existing PPLs
Of course there are very likely to be other ways to provide encouragement and 'aftercare', I'd hope that the GA training industry would continue to explore ways to enhance their activities. (There are some clubs/schools, I know, who do provide schemes for experiential flying opportunities for both students and 'graduates' of their training facilities.)