From a historical perspective, isn't that what British ships normally did? I mean switching to "Fire at will" when the first fully loaded broadside had been delivered, to keep the firing rate as high as possible? At least that's what I remember from my Hornblower books. Given that it would make sense in the game to have continuous fire not be less-effective than full broadsides.

You'd take the time for a full reload before the engagement and in any lull of the battle, but as long as you have a good target, you just fire away.