Or, instead added AI RNG into gunnery, just add another toggle like we have for convergence and fire mode, that changes firing speed. Set it to arbitrary numbers that would give 1st rates an option for a 3s broadside, a 5s, and a 7s. So you line up for a rake, set your convergence, fire mode, and then firing speed.
Smaller ships would obviously have even faster firing speeds, given the number of guns.
Perhaps even decrease accuracy based on the speed you're trying to fire the guns at, the faster you fire, the less time you're spending waiting for maximum accuracy / the gun to be dead on target, therefore you lose accuracy at the expense of RoF.