Lots of interesting stuff on this thread which, to my mind, proves two slightly contradictory premises:
1. the PPL syllabus has been proved by time and works well
2. we should never close our minds to innovation.
To go back to the original question, I would not normally teach pfls prior to solo but I have done so - with those rare students who learn to fly before their 16th birthday - therefore it's not hard and fast by any means. Those of us who have instructed for a long time are only too aware that the PPL course is basically about showing the student how not to kill himself by avoiding the traps that aviating encompasses. 45 hours is not nearly enough to teach anyone to fly in a meaningful sense. We hand them a bucket full of training and hope that they replace it with a like amount of experience as they progress as licensed pilots. At the end of the day, I believe that it's down to the individual relationship between the instructor and student as to how one progresses through the syllabus.
Teaching people to fly is one of the most rewarding things on the planet. We are a very fortunate group of people.