Almost all cabals require a note to be send, but not always do you want to play a character that can write.

So my proposal, let there be some writers guild in some town, so if you play a fee they can write a message you say and then deliver it.

My other idea is also roleplay based..

Let us buy books with empty pages, lets say it contains 20 pages and you can write on each of them, if you fail you dont destroy the book. Just makes it unable to see the actual page you wrote on.