Any form of P2F scheme needs to be banned by the Regulators, together with any form of anti avoidance scheme to circumvent the rules.
Once fare paying passengers are carried, then it is only equitable that the newly qualified FO is paid a salary.
Any ATO who associates themselves with this type of scheme must be treated with great suspicion and must declare just what financial arrangement has been entered into to encourage the unsuspecting customer (student) sign up to such a immoral scheme.
Even if you complete a P2F scheme, you will more than likely be let go, for the next junior birdman to be sucked into P2F.
Any reputable operator will simply not contemplate such an arrangement.
There are sufficient horror stories in the public domain to warn off any intelligent person from contemplating this rip off.
ATOs reputations deserve to suffer if they encourage P2F