I've thought about it before, but i think the 'missile' system we use is sufficient for realism bullets. Like
-set missile gravity on
-set self-destruct upon contact with the world on
-bbox size if possible, less than 1 unit wide
-set missile speed to 19200 (600 metres per second approx for a small weak machinegun) [used for shotgun fake trail in my visual mod already]
-Damage reliant on bullet speed, but set the initial speed value as a mod of '1.0'
Non-added features [to be coded]
-'Air friction' that deceleration is a "fraction" function rather than a "constant" sum [unlike land]
Other
-Have a simple sprite or small model for the bullet, have a yellow streak for the short trail system
It isn't that hard honestly.
But then comes the mighty evil projectilenudge. Pings higher than 50 probably won't see it appear, or when it appears, it'd be several thousand units away... hence graphics are almost pointless.