.. Started work on a system for the player to send messages to other parties or towns on the world map.
That's certainly interesting, depending on what the messages are 
Right now I have it so that you can send messages to kingdom hero parties only, I'm still working out the bugs and features. The system works as follows:
1. from right click context menu on world map, select a hero party to send your message to.
2. behind the scenes, the message context and tone is worked out as to what faction, player relation, etc. you are sending to.
3. next you fill out a presentation with numerous check boxes to indicate what subjects you want to include in the message, things such as trade, hire, attack, give gifts, follow me, bribery or other kingdom management tasks.
4. next you get to review the actual wording of the message, which is build in a script from all the choices you picked for message content.
5. You send the message and a messenger rides out to deliver the message.
6. upon arrival, the messenger delivers the message and any immediate consequences of that message are handled (such as trade or travel orders).
7. the messenger returns to your party with the reply, if any.
I have about 20 or so different message items at the moment. Only the relevant ones will show up when you build your message, so you may end up with only 5 to 10 choices depending on who you are sending a message to.