I have exhorted the merits of this idea in PPRuNe before and had virtual rocks thrown at me from every angle. Perhaps it was the way I wrote it, but I still believe having PPLs teach PPLs would not bring about a loss in training standards provided the PPL had the experience and the qualifications to teach. Who would it be more valuable to learn from? A 1000 hour PPL with a fresh G3 IR, or a 200 hour CPL with a fresh G3 IR?
Private instructors would not be inclined to run away to the regionals or multi-engine charter companies and take all the instructing experience with them. Having young CPLs do that on a regular and predictable basis is what is causing instructing standards to slip, because they are replaced with someone of lesser experience every time. It must frustrate the CFIs too, because they have to start again every time it happens.
Bring it on!
Walrus