Doghouse
I don't favour the idea of developing formal courses as I suspect this would make it to easy for authorities to prevent access to farm strips, etc.
You're probably right. A rating would be the wrong way to go, but structured training is needed, I think. Whether that training needs to be given by a CPL is a different debate, but personally I think that it is not necessary. Most of the instructors from whom I have learnt this type of flying have never sat the CPL theory exams - they have restricted CPLs based on their previous PPL instructor status. Conversely, many (but certainly not all) of the younger CPL / fATPL holders don't have the experience or inclination to give this kind of training.
poetpilot
I think the PFA facilitate coaching in skills beyond the PPL - e.g. tailwheel, strip sense, exploring the flight envelope etc.... - but I have a feeling this applies to people who own or part-own their own aircraft.
Wouldn't it be good if that sort of coaching was available without having to buy the aircraft first? In most parts of the UK there are almost no opportunities for new PPL holders to experience "grass roots" flying.
When I had a new PPL I would have jumped at the chance to fly an interesting aircraft with an experienced pilot / coach. The only "interesting" flying that was readily available was aerobatics. That suited me fine, but lots of people don't like aeros and the options for them were a bit limited. I know that a lot of people I knew then either don't fly any more, or are still flying between the airfields they visited during their cross-country training.
FFF
Yes, there are places like the Tiger Club if you look for them. But you have to look pretty hard, and there aren't many (any?) other clubs like it.
You're right about it being a question of supply and demand. I think the demand for simple fun flying is there, as shown by the increasing popularity of microlighting. I think that same demand would be there among flying club members, if more of them were able to see and experience different types of flying.