Hehe, I've had the same sort of thoughts, though doing anything that comes even close to replicating Daggerfall properly is probably too big and ambitious a project for anything aside from a major game studio, unless you managed to pull together a lot of dedicated and organised people. Though that might actually be possible these days... not likely, but possible.
My plans are not very ambitious. In fact, and because my free time is limited i was planning to release a couple of small mods for Skyrim first, inspired by Daggerfall.
Converting Daggerfall musics to use in Skyrim.
Add some notorious guilds that never made to the game like the prosttutes guild and the temple of Dibella (i guess this would have to be a mature mod with a 18+ years warning).
The merchant repeatable quests were awesome and i'm planning to add them to Skyrim.
Eventually when i become confortable with the tescs i may adventure myself with reproducing Privateers Hold and build one or two major cities, like Daggerfall, Sentinel or Wayrest.
Somehing i'm not planning to do is to put everything in the same world map. I would rather forget the idea of making a continuous landscape and put each major city in it's own world map. What would be the point anyway? Skyrim engine can't handle the huge land area of Daggerfall and this way i can build realistic sized cities that match the original size and add areas of wilderness around cities for those who like to explore outside towns. Anyway this is the idea.