What do you mean by "all the creative work is already there"?
Much of Daggerfall's content was randomly generated by the game engine. The character skill set is enormously complex, and would probably be very hard to do with the present game engine. The game worked with 2D sprites, so there's no 3D stuff at all, so every object in the world would have to be redone from scratch.
And, if that weren't enough, it's my understanding that the original source code to the game has been lost.
By that I mean: the scope of the game, the content of the story, the focus of the mechanics, the specifics of the requirements (like: what guilds, what do the guilds do, how do you advance, why should you advance).
Even if the source code had not been lost, every graphic would have to be redrawn, every object recoded, every mechanic re-implemented and rebalanced. You might think that's almost all the work. But as a developer myself, a large chunk of the work is just getting a clear picture of WHAT WE'RE DOING and WHERE WE'RE GOING and what the end result needs to look like. For Daggerfall, that's already generously done.