someone did make a working ship mod. it's a big ship with an attatched rowboat, it's a little glitchy, and the movement isn't very boatlike, but it does work. not anywhere cool to go with it yet, and as far as i know, no way to put anyone else on the boat. but it has an interior and everything.
i'd like to see either a future tes game or mod that has a vast archipelego, no fast travel, and a variety of boats you can purchase, as well as npc's to hire as crew. basically you need x number of crew members to run the ship, a navigator that you would talk to and say, plot dots along the map to show the course, then you'd be able to just sit back while the ship sails, maybe bring along some sort of trainer, or training devices so during the voyage you could knock up your blade skill.
and other ships out in the water that you could hail if you get close enough, and of course pirates...basically bandits on ships.
and distant islands with powerful items gaurded by even more powerful creatures.
maybe add in a mod to make some items high demand items on certain islands so you can purchase say 12 crates of apples from island a and sell 'em on island b for a hefty profit.
dare to dream, eh?