Hows about you look at the purpose of the flight.
If I want to fly for my own pleasure that's a Private Flight yes? Not if I hire the aircraft or pay for an instructor to accompany me it's not. Do either of those and you require a Transport category C of A and the instructor needs a CPL and a Class 1.
Take driving lessons and you don't find the car having to be maintained differently or the instructor having to have a pUblic Service Vehicle licence and medical.
If the aircraft and instructor are safe with a Private Cat, a PPL/FI and a Class 2 they don't suddenly become unsafe simply because the instructor or the aircraft are being paid for.
CAA discovered that aircraft that had been released to service when not in compliance with their C of A (unauthorised mods, AD's not done etc). Instead of investigating why the engineers they licence were doing this they invented the Star Annual where the aircraft has to be taken to an M3 organisation every 3 years so someone else could check it over.
Any decent Quality System investigates and fixes the cause of the problems to prevent them recurring. It does not simply ignore the causes and treat the symptoms. (I speak as someone who runs an ISO 9000 registered company)
These are two examples of unnecessary costs that could be reduced without compromising safety simply by using a better approach.
(Lest I stand accused of slagging off engineers, I am willing to bet that the signing off happened because the information they needed to determine airworthiness was not readily available to them in a concise and easily assimilated form)
Mike