I think it sounds like a fabulous idea,
tp, and I'm not just saying that because you said it.

It would be sort of like what some military personnel do before dangerous missions... write a final letter to be forwarded in case they don't come back. Would werewolves be included in the letter writing? In case of a lynching of an actual beast (boy are we bad at that

) would a letter be found on them sending people in all kinds of wrong directions?
Picture last game, and say that
the phantom was to get lynched first. A letter is found just before they throw his corpse into a graceless heap on the edge of the woods, and it reads something like this:
If I had only had the time to tell Fordim who should die...
And nobody is aware that Fordim is innocent. It would add yet another layer for the players to unravel.