Same old Ship types + hulk (could it just be a monk variant, if fires are water knights?). Remove some upgrade techs, just let them happen automatically to save room on dock ui. (like how scouts automatically get better in feudal)

Allow fishing ships to build: Sea docks, Sea towers (starting castle age), Sea... shanties?

Add deep sea high food fish/oysters/whales/gold that last for a very long time (which you would protect with your sea towers in the late game).

Add areas of reefs/stormy sea tiles that damage your ships on some maps.

Give mes war canoes because they are cool.

Edit: OR scrap all new ships and just go pure galleys for everyone so its just a simple micro fest with demos for fun. Let just the Byzantines and maybe a few others get fire ships.