We had something like this in Makar years ago, where absurd goals like "sack shanandoah" were handed out.
I think you've probably misunderstood. If you reread, there's nothing like saying "Sack Shanandoh" -- or indeed any sort of movement on the world map. I apologize if it wasn't clear enough in the initial description, but the legendary quest would be a self-contained event. Just like a tournament takes places outside the normal movement conventions and activities you can do on the world map, so would the quest.
Why does this need to be a feature, and not done by RP
That could be said about almost anything in the game. Why bother to have a game mechanic that runs a tournament when you could just ask everyone to gather in Perdan and duel each other to surrender? You have a real tournament because people enjoy it. By making questing an actual feature it gives structure and makes it real. Also, like I said in the benefits, it gives it an actual extra game event for people to enjoy and have fun with.
Why not allow priests sufficiently well ranked in the faith to do this,
Yeah, that's fair enough. In the spirit of the idea, that makes a lot of sense.
