The first national attempt to change the system was in July 2013, before the CAA went through its perestroika session. Agreement to go ahead with the LAPL/PPL WG didn't follow until much later.
Why 6 exams? Well, if you take out RT theory and that 'headshrinker horse$hit' of 'Human Performance', you're more or less back to the way things were before even JAR-FCL came upon the scene.
Also, the 6 exam format agreed closely with the days of CAP53, when a more structured theoretical knowledge requirement was in place.
As for 'sittings', the long term objective is to get rid of them as they serve no useful purpose. But that cannot be achieved at national level alone.
Are you the vendor of the iToy exam 'app', or what?