All in all, a good idea. Once upon a time in DoD 2.0 there was a similar "group" created where people would sign up and then use a tag to show that they were team-players, but damned if I remember what they used.
You could, with a microphone, broadcast your willingness to team tank. I've done so on some servers, and with mixed results of course. If you get a driver who is not sure of what they are supposed to do, and won't listen to the gunners, you die more often than not. That's life.
I think that this tag really is just to show that you are willing to work with whoever and not drive you off into a minefield on purpose or yell at you to get out which is about the most childish thing I have seen. having a microphone helps but not everyone speaks english. Having TT tags just means you are willing to work with the commander however commands are given, hotkey or voice.