Oh go on then I'll reopen the old thread.
Instruction is a profession. Get over it. If you want to teach canoeing, diving, walking even underwater basket weaving then you need a formal qual. We all unanimously agree this to be FI(A) or CRI
However if you want to earn money then you should quite simply be a professional pilot, anything less is exactly that, something less in reality and fact.
Simply put IMHO if you haven't got a CPL or ATPL you should not earn money from instruction period.
Now whether or not the syllabus to achieve CPL is relevant and useful for those intending the FI only track, that is a whole other opinion. Before the shouting starts I do think that there should be certain grandfather rights and transfers for those with certain levels of experience (separate debate as to quanta) for a set amnesty period of say 24 months so we can clear up all those with old/unusual/foreign/military/etc quals BCP, UK only licences, QFIs, etc but after that simple anyone new in should be a professional pilot
AND and FI/CRI IMHO.
For those thinking what does mach tuck, thermodynamics and polar stereographic charts have to do PPL instruction? Think where the students you instruct may one day end up.
Primary school teachers have degrees, secondary school the same and so do university lecturers. Do you not want people to think of flight instruction as a profession? If you do then get a professional qualification and leave the amateur stuff to showing your mates around the skies on bank holiday weekends.
Now whose first?