Arma voice chat is used for the server, but teamspeak can be used for out of character communication. It’s pretty simple to use, double clicking a channel switches to it and double clicking a user opens text chat with them. There’s also channel text chat which can only be seen by people in the...
Technically they haven't opened GTA 5 up for modding either (as seen by T2's attempt at shutting down OpenIV....), yet FiveM still happened! All depends on whether proficient devs are up for the challenge. I know https://nanos.io/ are looking for new multiplayer projects, maybe tweet them...