Player and NPC mouth animations could be because they could have dialogue that has voice-overs with a tone randomizer (sort-of). But I feel that in-game VC would be a great idea. Complaints will come in as well, and you will have people very for and very against it. I am for it, but I think some servers would have the ability to toggle VC on or off in this area or that one.
I have a solution. Since a friends list is confirmed, why not have it so that only friends can hear each other? I think that would be best. Then only people you trust would be able to talk to you . I actually can't believe I came up with this idea