Personally, I'd like to have a Morrowind/Oblivion scale map. I feel that it can be filled out so much better, and not having to travel forever to get to a cave would be all the more awesome. I'd actually like it for the game to be created fully to this standard, and then for more to be added between the finish date, and the release date, if possible.
I would like to be able to leave a cave, and see a ruin on the other side of the area I'm in.
Also, remember that a good landscape can make the game feel so much bigger (look at Morrowind/Oblivion), and I think Skyrim would be a good mountain-ey region for this, if used.
If you want to argue about fast travel, randomisation, or something not world size, I redirect you http://www.youtube.com/watch?v=l1wBdj30pBw.
P.S. If you want slightly bigger than Morrowind/Oblivion, or something slightly smaller than Daggerfall, You should vote for one of those, and post what you think, Something In-Between is really for a middle between Morrowind/Oblivion and Daggerfall.