I appreciate the argument for paying and I don't feel informed enough to say yes or no, so would definitely appreciate some clear, unbiased information. Honestly speaking, I know I'd resent having to pay as footpaths feature plenty of gravel, styles, kissing gates, etc. and hikers don't pay for those. That's not to say that I wouldn't pay if I had to. I did once refuse to pay at Aston Hill. A fiver for a few miles of trail is pretty raw, in my opinion.
What I would really object to is the destruction of existing, unofficial trails on these sites, leaving no options to ride but official routes. Haldon is a good example of this where everything is being destroyed and seemingly replaced with flat, smooth, metre-wide gravel paths. I can appreciate why structures (ladders) have to be removed, but otherwise it's just the ground without so many sticks and leaves in the way, so leave it alone.