This could be written as an external program, it doesn't really sound like something Blur would add to JJ2+. It should be server-only though to prevent another "Project Omega" situation from happening (I have not been playing JJ2 back then, but from what I heard, nearly everyone was using Project Omega and chat was flooded with the automatic messages).

As wKtK said, there should definitely be an option to turn it off or mute it. Sure, it would be fun for some time, but after a while the messages would get very annoying and spammy, as with all multiplayer chat bots.