Hi,
no it will not be possible as emotes normally do not write anything text wise to the chat, isn't it?
-> That's how the NPC addon works. It detects the text in the chat and then silences the general audio volume (same as you said, that makes your effects and other music etc. silent then).
At least that is what I understood it does last time I saw it.
So basically your request would only work if you get a chat message if anyone around you plays an emote or mounts (those loud blinking mounts...)
Addons can also only react on stuff of other players if you are grouped, at least for most stuff.
I doubt there even is any API to detect if anyone, you would have the mouse cursor over at the moment the emote starts, starts to play an emote with music etc.
Basically ZOs wuld have to implement such a sound setting, or you'd have to be quick and run away the moment you hear one
