well, I think Voice would harm the RP a bit... A lot of people would have trouble making their accents right, or in my case, lacking the ability to change my voice to the occasion.
as for typing, It would be great to make talking In game realistic, where your voice carries so far, varying in each character, and have the text become more incoherent the farther you get. (so a smaller characters voice would be softer, and a larger characters would be louder). That way, you could pick up bits of a conversation, and maybe you would hear more from the dwarf than the halfling. And a eavesdropping skill would modify what you hear.
and the shout command would carry a good distance, and not through the whole server. It would be interesting to hear a cry for help, and you have to look for it.
just some thoughts.