"Might the PPL performance syllabus/exam now be ‘beefed up’ & a stand alone paper be adopted given the circumstances revealed in this Troutbeck accident?"
I don't see any change to rules or examinations being relevant to this accident. Especially after the warnings before the flight attempt. He knew it was marginal. He failed.
(Many years ago, with a heavy pax, in a similar situation, looking ahead, I aborted after lift off and hit the fence. No injuries. Repaired and flew out solo a few days later. I might have continued and not succeeded.)