The main problem, as I see it (not knowing anything about modding this game) is adapting the game "module" itself to work with NPCs that have schedules and days that do not last forever. One would likely have to rewrite some dialogue and alter various quests and scripts, since the current game has been written with the assumption that these things do not exist, and that NPCs do not have daily routines. Of course, I haven't actually played the game yet, so I don't know the extend to which this is true.
If the quote I cited above is accurate, the technical details shouldn't be as much of a challenge.
