Voice chat would be very nice. I agree with some other users saying it has its downfalls, but here's my input;
You can choose your language. Therefor language shouldn't be a issue. I also believe you should have your own deafen/mute for a user if they're doing something wrong (saying swear words n stuff if you don't like it), or the server creator can have their own deafen/mute for a user.
I also, however, believe there should be a option in the Server Settings to where you can enable/disable voice chat.