As it is highly likely a modder would like to add the new tag to his highly modified MercProfiles.xml, without having to manually insert and edit that stuff 255 times - you can use regular expressions with Notepad++. In the edito, press [Ctrl] + [H], seach for <ubFaceIndex>(.)</ubFaceIndex> and replace it with <ubFaceIndex>\1</ubFaceIndex>\n<usVoiceIndex>\1</usVoiceIndex> while the option regular expessions is ticked on. Then replace all in the file, this will create the new tags. The (.) part searches for one symbol and stores it, \1 then places that previously stored symbol. You then need to repeat that with (..) and (...), of course.