Interesting idea -- but IMO this isn't one that absolutely needs a unique ship model to be implemented (that is, should we decide to try making some ship variants like this). What it requires is the ship be set up with the appropriate battery structure in the game itself. I'm actually not sure if that's possible or not, since I don't deal with the gun and effects handlers -- just the ship models themselves. I'll ask around.
I do have to point out though, that generally anything ship-related from O'Brian's Aubrey-Maturin books is going to be too modern for a game set in 1720. The specific idea of a ship with multiple batteries of differing weights on a single deck, however, dates back to the creation of naval artillery.
Also, I've been snooping around from time to time for more visual documentation on Ottoman vessels of the period -- an idea that rather fits here. My luck has been mixed and I'm always open to additional resources on this topic.