It makes the show more interesting to have roles like The Seer, but they should be incorporated into the show either right from the start or after the first week.
I still think an Assassin role would be brilliant. A player (serial killer in WW) who is neither faithful or traitor. The Traitors kill every other turn, they still make a selection but it won't go through. Instead the assassin chooses who to kill.
The assassin can also jump to a new player but only once after the assassin dies. (the assassin nominates a player each evening who they want to be their successor).
From the Faithfuls perspective they'll think it's a normal game. But the Traitors will know something is up after the second day when their murder doesn't go through. There's also the possibility that the assassin could name a traitor as their successor too. It'd be glorious.