Well, one way of looking at things would be to accept that those who instruct for a living, should be professionals, and should hold a professional, commercial, qualification in order to do that, …it’s called a CPL!!!
We are not talking about teaching people to drive here, and even that requires a commercial licence and course of training prior to starting the instructors course!!.
The restrictions applied to microlites etc put them well out-with the realms of what we are talking about here, so lets just leave that particular sport out of the equation ( I do accept that it has some very competent and enthusiastic instructors..in its field)
Mickypitch, to say that you have ‘looked’ at the ATPL course notes (there are around 17 manuals!!), and find ‘little of relevance’ for instructors is frightening…. in the extreme!!!
If you guys think that you know enough to teach after reading your Trevor Thom books and passing your PPL ground exams , then heaven help us all! The level of prior knowledge required to get through your FIC is a lot greater than you seem to think,in fact it is staggering,... and so it should be.
Now even under the old CAA system there was not a vast difference between CPL and ATPL ground exams so don’t think you are going to be in for an easy ride when someone finally does offer a long overdue CPL theory course, (and yes, there should be one, for the reasons outlined by Genghis)
Before you make any more assumptions about the level of knowledge required to teach effectively, sit down with an instructor and find out just how much he/she knows, and how often that knowledge is used.