I think you've hit on the point that has kept many experienced PPLs out of instructing - the need to demonstrate CPL knowledge - eg: CPL ground exams or 'better'. However, I think the CPL ground exams were a pre-req long ebfore JAR, or at least in the early 90s. At that time, once you'd done the 10 and 6' grouping of the old CPL exams, you suddenly suspected that the Class 1 medical at the start of the process was actually to see if you were fit enough to do the ground exams.
The 'interesting' bit about the JAR pre-FIC course requirements must have been the discussions around the JAA table leading to them - a real committee award effort by the look of it!
