I have beaten the extreme parkour a few times now, and every time I beat it, I always think there should be a prize. Make it so if you beat it you get a grass block or something... Me or someone else could custom code a plugin so you only get 1 a day...
Donors 25+ would get a free prize daily due to their /jump. 20 dollars would get you fly and literally the same result.
A simple 5 minute worldguard fix can be used to disable /jump. Fly can't be disabled though I believe, so a plugin would be necessary, which is likely not going to happen since it'll lag the server and takes time to create (fly-disable would be easy though).
Sometimes mods hold competitions. I was in one where 1st place was any ore you wanted and 2nd place was 15 iron blocks. And I was told the prizes get higher. Also, hax.