Underwater city, where u have to find gear or spells to get to. A city in the sky, where you have to find a special plant and potion then you grow plant like a bean stalk to climb to get to..An Island You buy a boat, repair it and upgrade it, find a crew to sail it, to get to the city on the island, possibly several islands. You sail the ship, repair it, fend off pirate raiders, u have harpons and some kind of canons u can use for defense or attack. Can steal supplys from other ships. Explore the ocean, kill megaladon sharks or sea monsters..maybe even a trip to the center of the earth to a ancient hidden city.

I think you might want to go to http://www.gamesas.com/topic/1608862-tes-vi-location-and-setting-speculation-34/

Yes.
There's also http://www.gamesas.com/topic/1606956-official-beyond-skyrim-tes-vi-87/ for more general suggestions.