Adding a simple option to be able to chat with team only would be great in PvP/CTF. Since you can party only 4, its difficult to coordinate with the 5th when you are doing an actual 5vs5 game. Especially when all 5 aren't from the same guild, you either need to PM or say it out loud.

Maybe /team or any similar command should allow you to chat with only your team, whether red or blue. Should be easy to implement.