So, the private IR pilot has a strong interest in not making the demonstrated competence any lower.
10540
I like the suggestion here of a modulated IR with a Basic PPL/IR which can then be upgraded to cover the whole CPL to ATPL.
the flight test would be No different the only difference would be in the ground exams. There would be a specific exam/ set of exams designed for the PPL who is not flying commercially, who will be using LAS and has no aspirations to be a heavy jet pilot flying at FL390.
The flight test and standards would be the same but with generous allowances given to PPL IMCR pilots. The litmus test is the test itself. Either you are good enough to handle all the IR test requirements or your not.
So the only quality difference between the two would in reality be the exams you have covered but even there you could always upgrade as and when you need to be a commercial /ATP pilot.
The powers that be may actually like the idea of the building block scenario of what they already have rather than a mickey mouse stand apart IR for private pilots.
Pace