I have to say, from a realism point of view, shutting down the engine cannot be more true to life, but what will the commision of enquiry think of it? Bloody stupid idea!
On my second PPL renewal, the examiner did just that to me (pulled the mixture) inspite of my warning him beforehand that if the engine did die, I'd treat it as an emergency. I terminated the test there and then, and returned to the field, where the examiner was treated to my grumpiest style of disagreement. (before my CRM course!
)
I tested the next day with a proper instructor, and passed!
Now that I am an instructor, in the pre-test briefing, I make sure that the candidate is fully aware that if the engine dies, we have a full emergency. I don't even simulate the engine failure after take-off at our base, because of too many houses nearby, I prefer to do it on the Go-around from either the forced landing or the precautionary.
As an aside, the local parachute club had a couple of jokers who liked to take the keys with them as the dispatched, until a rather large Irish mate of mine was flying. On the completion of the successful landing, the skydiver spent a weekend in hospital for wounds recieved during the "de-briefing".
In brief, don't do it, and don't fly with those who do!