I've created a plugin if any of you can use it let me know. Im not sure if this is planned some "plugin" repository somewhere, so Ive just uploaded to my own homepage.
The plugin allowes players to create "chat channels" and joining them. This is very basic and hackish, but it works without any clientmodifications. The idea is that eg. people from a CTF team, such as BAR can speak "privately" dispirte of which team they joined (red,blue,observer etc). I've got a few ideas on how to enchange this, but Im not sure if anyone but me finds this plugin useful. One of the aims with it was to try the BZFS api

ReadMe.txt hopefully clarifies what it does.
ChatChannet can be downloaded here (source + Makefile + linux .so)