Differences training is a complete red herring - you can learn in a Malibu if you want - or follow Caroline Graces example and learn in a Spitfire (excuse me while I turn green with envy!!), but it seems to me most of the people on this forum would have been throwing up their arms in horror at that suggestion.
To go back to the ORIGIONAL subject, the NPPL is a great idea, but where are you cutting back on the training? You can cut some of the instrument training, but this does not give a 10hr reduction, cutting back on the Nav is not a good idea either as I thought this was an area I understood the CAA was concerned about.
If they restricted the NPPL to say 25 miles of the departure airfield and under the supervision of an instructor (ie. as if it were a student but allowed to carry pax.)then it might make sense, but to just reduce the permitted hours whilst allowing the same freedom to get lost within UK airspace seems nonsense.