A number of other forums run trackdays at some of the smaller/cheaper tracks quite a lot.
CS.net trackdays that are open to non CS members (and therefore not just Clios) should fill up fine. Maybe open them up to booking for CS members a month earlier and with a little bit of a discount so that we get a good fleet of Clios though?
How do the Mazda on Track and Lotus on Track ones work? I think there open to non members/Lotus or Mazda owners, arent they? Maybe get a joint venture with other Clio/Renault forums?
There has to be a viable business venture in there if its done properly, as there are lots of small indipendant trackday companies out there who seem to be surviving year on year. I have actually wondered about how you would go about starting one of those companies in the past... Organising trackdays sounds like it could be good fun (obviously theres the nightmare of admin, but at the end of the day you get to spend a lot of time at tracks with like minded guys).
Theres a big difference between hiring a track and spreading the cost between mates and forum members, and actually running a 'proper' trackday company with numerous events, though.