I believe someone at Beth has already thought about an RPG like that. The fact that it didn't happen should say something about the "promising" success.
Not really, it mostly just say that it did not happen yet.
For the rest of your post...sure, d&d and the d20 system is probably a wrong choice to emulate TES but thankfully, there's plenty of other rpg system out there. By the way, many licensed games are not d&d-based, unlike what you seem to think. Of course, video game that carry the d&d license will use the d&d system, if not, why bother with the license at all. As for game based on d&d? If what I read is true, TES are based on on of the dev d&d setting, making it...a d&d based game. Anyway, even if in most of the game player skill is what matter most, character skill still matter as it set how difficult a task is and the system has some variation between game anyway, like how in Morrowind there was a chance of an attack missing even if the player had hit.
What I'm trying to get at (poorly), is that saying that it can't be done because it would abstract player skill into a die roll is a bit like saying it can be done because the gamemaster will decide what the guards say instead of repeating that they took an arrow to the knee.