Recordings are really not necessary, but could be done in mp3 format, in a separeted file.
Also there must be a function to mute/unmute in-game.
And invitations to voice chat could be via in-game chat, like for example:
A certain command enable voice chat + f# (for player # in chat order)
The player "Nickname" is asking you to estabilish a voice chat with him, do you want to accept it? Press y, if yes, or n, if no.