I like this idea, but may I tweak it??
AJ (Animal Jam) has a message system (Jam-A-Gram) that has literally choose what you wanna say, no typing. Maybe FH could have the ability to type??
Second..
Maybe instead of a message, there could be certain option for something like this:
You click on a button. (Let's say for now that it was.. hmm.. a stamp.) The stamp lets you write in a letter that will pop up on the other player's screen until they hit a green "Okay" button at the bottom of the screen. It could certainly be abused by troublemakers sending spam, chain mail, and harrass letters, but maybe there was a limit to each letter you could send, maybe one to each person every fifteen hours??