I can imagine the Watchers working best in a world with more overt magic. So then you could have a whole society under a geas of some sort that prevents them from misusing the Chronicles. Magic might also explain how they are able to track these superior warrior types for so long without being caught. Maybe there's something in the tattoo? And somehow it got messed up on Joe's wrist so that he wasn't bound the way he should have been.

Regardless of the universe, though, you could actually have a pretty interesting story that casts Joe Dawson as evil, doing his best to destroy a society because he can't deal with the rules that while harsh are the only way for them to survive. And the Hunters probably weren't a new invention. For that matter, why should they be? If the prize is ruling the world, then it makes sense for the humans in the know to try to influence the Game.

I also have an image of Duncan in a thousand years getting together with his watcher and his watcher going, "do you actually know Methos, the 5,000-year-old immortal?" And Duncan pausing with his glass half-way to his mouth, "5,000 year old? To my knowledge, he was 5,000 years old a thousand years ago. Exactly how long has he been referred to as 5,000 years old?"