I never used the internal chat. For years I have been using teamspeak for stuff like this. And recently also mumble which is an open source alternative. I hear discord is popular as well for general team communication (but discord is the usual "we can spy on you, do anything with your private communication and it even belongs to us. Just do it, usually it won't matter. <evil snicker>").
The reason I'm listing all these alternatives is that at least the first two have the advantage of multiple channels you can switch to. It may be a little less comfortable since you probably need to alt-tab out of the game for a moment to switch between the channels (if you don't have two monitors), but it should work quite well apart from that. And you can still use the game internal text chat as a low-tech global channel while you are split into different voice channels
I don't think you can hope for a mod to do this before the game is out of EA, if at all possible it would need serious programming effort. And I don't think TFP is doing anything with the internal chat as it works well enough, they have lots of other fish to fry before release and it isn't even clear how many really use the internal voice chat.