I think a dummy style is usually used to accomplish this, but it would definitely make sense to apply to a whole level pack. You could imagine, for example, a pack designed to use the sounds and music from DOS lemmings benefiting from the ability to change the exit sounds, hatch sounds, all sorts of other sounds, etc.
Though I think at that point you'd almost want some sort of generalized way to overwrite arbitrary sounds from the base game, but I'm not sure how much effort that would be.