A37575, going back to your opening statement:
I thought CASA had banned mixture cuts on take off following the earlier Duchess crash? Either way, that technique is fraught with danger of mishandling by either the instructor, the student or both. These two crashes and others before them prove that instructors should not risk the lives of their students with dangerous practices in attempts at realism.
What does using the mixture have anything to do with the student losing control? The same thing would have happened if the throttle was closed. I'm sure you've got some very good experience and teaching techniques, but you're arguing the wrong point here.