Voiceover, if added, then so that it can be turned off in the settings.
Why not?
Make 2 versions of soundlib, and when game starting, chose one of them. Depend of settings.
In first there is a full audio. In the second some parts is silent.
Or make somthing like $lang for voice. With loud of voice audio, and everityme, when voice-audio is calling in game, use $loud to change loudness of voice. Voice audio will be a new code strings, and it will be easy to insert $loud in every new code string with voice callings. It will be really problem to insert $loud in old callings soundlib. But easy to new.