I was going to suggest this idea, but apparently it's been suggested 4 times before, so instead i'll bump this with the idea that the game (or mod -cough- RTB -cough) should feature an inbuilt vent client, with at least 1 channel. Also with game server creation, if the host owns a vent server, he can enter the details so it will be interegated into the game, for those who don't have vent.
But I guess if there is away to use voice without vent, then go forth and do so (Also the if ingame build voice, it should feature a ban from the voice but not the server)