I have had an idea in my head for some time that we on the webDiplomacy side could integrate an instant messaging system for our press, which would mean that messages are both sent and received instantaneously when the press boxes are open and notifications are presented on the rest of the site without having to refresh the page or open a new page. This is a pretty obvious thing to integrate along with group messaging in my opinion - both are a fair amount of development work, but they go hand in hand. Either constitutes an almost full redesign and refactor of the press system, so doing one at a time instead of both together really doesn't make much sense if we're planning on using our limited development time and resources in a sane manner. Because this thread is regarding group messaging, I'll stick to that theme, but instant messaging really should be a priority when it comes to updating our press system.
Ideally, the way this would be designed from a UX perspective would be simple: there is a menu, probably a dropdown, with each country and a space sort of like the address line of an email where the name of the country you are speaking with is displayed. This would take up a small amount of the space that the press box itself currently takes. Aside from this, the display would not change. You can add multiple recipients to a message this way, just as you can add multiple recipients to an email. From a design perspective, this makes the most sense.
I don't envision changing the standard country-by-country toggle options that we currently have above the press box, but we would need a way to access previous group chats without necessarily remembering all the members. I propose replacing the notes tab, which I personally have never used and don't think many people do, with another dropdown containing shortcuts to each of the group chats we have been a part of throughout the game. If we haven't initiated any or been invited into any, the dropdown would simply be empty. In gunboat games or public press games, this tab would simply remain the notes tab.
On the front end this would not be very difficult to code. Rearranging the notifications system on the front and back end to allow for live updates would be the trickiest component.
I can probably draw up some basic design thoughts with pen and paper if it would interest any of the developers here. My PHP is absolutely atrocious, so I wouldn't be much help on that front.