A couple ideas just occurred to me, first and the one that fits this mod the most, a few new ships the over-all ideas of which I'll list shortly, the second idea is a combination of a mildly inaccurate historical reference and joke, a couple pirate ships that instead of being modified Musashi ships are labeled as pirate designs and are inspired by German and British destroyers(since subs aren't currently an option).
Back to the first idea, the over-all ideas are: an early battleship or two, a heavy cruiser, and a heavy destroyer
-Early battleships as I imagine them would be inspired by pre-dreadnaughts having 2 large ballistic mounts, 4-6 medium mounts, and several small mounts, while also being less armored than "modern" battleships like the Amaterasu
-the Heavy cruiser, the general idea being something faster than a battlecruiser but not quite as powerful, while still having more medium and small ballistic mounts than the other non-battlecruiser cruisers, perhaps a new medium twin gun turret could be added as it's intended main armament(a 2 gun version of the Kitsune without a range finder?)
-the Heavy(or maybe it should be labeled "advanced"?) destroyer, an abnormally large and heavily armed destroyer of comparable size to the Gongen, with the ballistic armament of the Kisshoten, but also having mounts for 2 medium missiles as well, while it may be big and well armed, it's still a destroyer and as such has poor armor for it's size(compared to it's cruiser counterparts).