What you're asking for is exactly what I discussed: A long-term conversation with an arbitrary, self-selected group of characters. This is not intended to be the normal form of communication in the game. It is exclusionary, and would open up some exploits/abuses. (I'm not saying you personally would do that, but these are issues that we have actually observed in the past, and some that we have identified as additional obvious exploits/abuses.) That's why this ability was specifically *not* added. Coding around these would be time-consuming and difficult, and the necessary limitations that would be added to prevent the abuses would cut into the functionality you probably desire.
It will not happen.
Open up your discussion to a wider group to include more of your fellow players. Form a guild/society and have everyone join. Get your ruler to create a message group.
