I am going to respectfully disagree with this sentiment... VOIP would absolutely be a HUGE positive for this type of game. Language barrier? instead of playing the VOIP, play to anyone who doesn't understand the language being spoken a garbled recorded blurb similar to that in Sims language.
Mic spammers and music blasters? Kingdom wide KOS order by way of the crown. Mechanically? Add mute as a point and toggle option.
Without voice, you miss out on all of the hyper interesting characters that make up modern day RP gaming. MMORPGs with text are quickly going the way of the dodo in response to games with proximity directional based VOIP. If you aren't interested in a built in VOIP system, maybe consider creating a pipe of coordinate based information reporting characterid and x,y,z and some teamspeak devs will easily be able to create a 3d positional based VOIP service for their locales.
There is just so much missed opportunity for such a common modern game mechanic.
Sure, not everyone is a professional voice actor/actress, but you don't have to be.. Being around great RPers rubs off on people and if you have voice, the RP goes to a completely higher level.