This is would be a killer idea for Events (Holiday, etc.) where the mystery and hunt for rewards actually makes sense. The problem with doing quests like this is it gets completed once, and immediately goes on the Wiki and then all that happens is people do the quest with two screens, exactly like Runescape.
But if the Halloween event was a prop hunt started off by reading a Bloody Letter and finding clues, that would be cool. People would run around the world completing tasks instead of farming Big Scarabs for 3 weeks straight. Real activity.