A long time ago, we were encouraged to pay familiarization visits to the tower from time to time. Some 'pilot style' controlling was the norm, and doing the occasional PAR talkdown was positively encouraged. The only proviso was that the qualified controller would ask the pilot whether he was prepared to accept a talkdown from a 'controller' under training.
Illegal? Probably.
Safe? Yes.
In turn, we used to occassionally take the controllers flying. Sometimes, heavens above, we even let them handle the controls.
So where do we draw the line? I much prefer the common sense approach that I grew up with then to the blame culture that we live with now. People used to exercise their judgement, and they were then prepared (and expected) to justify their actions. Do we live in a safer world today? I don't think so.