As the title states, make the tails of shot's 3D. Laxemann ha accomplished this in a mod, that could still be optimized, and it runs great. If this tech were to be added to the actual shot's we have now, it'd boost the Audio quality 10 fold. Essentially, it'd work like this.
A shot is fired, depending on where environment you are in, that tail isn't just an Audio sample played from your gun. Instead, the tail after the shot, moves through the environment. Doing this in Engine and not as a mod, would make it far less CPU intensive than a mod like Laxemann's Soundscape, however that mod even still runs without noticeable impact to begin with. However, if this even were to be the case, it can become a simple option in Audio settings for those who would like a 3D soundscape over the current static soundscape. It's a Win Win for everyone.