So this is kinda half class idea, half boats idea.
at first, you would be able to make small fishing boats from the carpenter. however, the blacksmith would be able to make the shipwrights adze for one steel and one wood. the adze would be the talisman for the shipwright. the shipwright would make modular ship parts that can be put together by workers to make ships. this would allow you to still have creativity, but restrict exploits and overly complicated physics.
side note #1: an adze is what a shipwright uses to bend wood.
side note #2: I have no clue what the shipwrights workshop would be.