I'm not a game dev nor trying to be an armchair one but I do believe it isn't *that* hard to have it implemented (or at least it isn't much computationally intensive): Supreme Commander had it with thousands of units at the same play field 10 years ago (e.g. a shell from an artillery piece can hit an airplane).
I think the change would be to have the bullet trace a random path inside with chance defined by circular error probable function, this function (that defines the ellipse that could be hit by the shells) depending on the factors currently affecting accuracy at the time of the shot.
So the shot is aimed at a target, it fires and takes a random initial moment based on the CEP function or whatever defines the precision, but then it "exists" and an eventual intercept with anything (i.e. wrong target) would trigger a ballistic penetration/damage test.