The main difference between the NPPL syllabus and the current “full” PPL one is the radio nav has been taken out. Those of us with CAA PPL (A) licences did not do this anyway.
IO540 is quite right when he says things take years. The PFA aspiration for the NPPL was to have a grass roots recreational licence. Training would take place on permit aircraft (in place now) using the existing PFA coaching scheme, on a non-commercial basis, from unlicensed, but “approved” strips. The theory exams would be changed to reflect the “recreational” nature of the licence. In essence, you would have non-professional enthusiasts, teaching other enthusiasts; in much the same way as the inspector system works for building a permit aircraft, or the BGA train pilots now. Work is still continuing on several aspects of the above, but progress is slow. The “full” PPL would stay for those of us who want to go the professional route or fly aircraft >2000kg.
EASA is actively investigating an RPPL, which is currently based on our NPPL. This will obviously have an impact on the original PFA view and I am not up to date on this aspect. The original idea, if fully implemented, would have slashed the cost of a recreational licence and vastly increased the number of pilots.
I do take issue with the “most pilots do not know if they want to fly commercially or not”. Obviously there are exceptions, but I think most people who start flying for fun, stay flying for fun. Such people are probably too far down their chosen career path to want to start over. I started off building control line models at 11 years old, but I never aspired to professional aviation and will ditch my current “full” PPL for an NPPL if the UK only restriction is lifted.
Rod1