Ships should be found, or crafted... if crafted, I suggest that 9 wood blocks make 1 "hull block" then, 8 hull blocks with a "sail block" in the middle (possibly crafted from 9 wool).
I really like this idea. But, I do see the potential dislike as there are shulker boxes. I think that they should give the same inventory as a saddle bag on a Llama. 3 to 9 depending on the craftin...