As they touch on in one of the quest tutorials on creationkit.com, the only issue with this is to make new files you need the original voice actors... or someone VERY close. Doing it is not the issue at all. In fact go over to the last few tutorials on the creation kit site related to quests and dialog and they talk about how to edit things like npc's hellos and goodbyes. The engine is built for doing exactly what you're talking about with minimal fuss EXCEPT NPC's talking with several different voices would be very odd. Actually, I'm more interested on focusing on non-named NPC's. There are common things said by everyone regardless of city, gender, etc. "Arrow in the knee" for example. I don't want to have people impersonate the named NPC's so that it matches... I want to have a mod that just adds a great deal of variety to the radiant dialogue (said mostly by guards, etc) but also yelled out my forsworn, necros, bandits and whatnot. I've exported all the dialogue and I know where the .fuz files are... just not how to throw my pre-recorded audio files from other people into the pool that the engine uses when assigning a radiant voice... "keep your hands to yourself, sneak thief..." that sort of thing.