Having just read through this thread I mostly agree with people. I think a lot of people would pay a subscription fee but I personally know of quite a lot of people who wont pay a sub fee not because they don't think it's worth it but simply because they are against the idea of paying for things on the internet.
My advice would be to offer additional things to paid members as opposed to taking away things from non-paying members. Say drop the PM limit for non-paid people to 50 and raise it way up for the paid people.
As far as race reports go, would a system whereby you can have the race results live on the web for people who either pay a subscription or paid a nominal fee to view to updates of the event and the daily updates. Then after the event is over make these reports available to non-paying members so paid people have the advantage of getting the same information just quicker. Obviously live results,etc would take quite a bit of organisation and it might get to the point where all the fun is removed from it.
More regional reports done by a select few would work quite well as long as the quality is kept up to oople's high standard.
One thing I would personally love to see more from the events is video footage but this is quite different from photography and would take quite a few more people/equipment and then somebody to cut it together afterwards, would there be the demand to film all of the national series and then release an oople dvd of the nationals?
Corporate sponsorship would help cover the costs of covering events if you can attain it by offering them in return advertising banners on the event coverage pages as well maybe a plug for them in the opening text and possibly a small watermark on the images?
You could try doing some deals with some model shops to have a %discount for members as well as then links on the site too the shop. (for example reviewing a kit or equipment and having a set of links at the end of the review of places to buy the kit within the UK that oople (paid?) members can get discount.)
Try and rope a few top drivers into having semi-regular blogs would be quite good to her the different drivers opinions on general rc car news and what sort of preparation they put into the cars comming up to major events.
Anyway thats enough rambling for now