Does one exist? Is it even possible?

Not that I'm aware.

I think the skills are hardcoded into this game, too. Otherwise we'd likely be seeing a huge number of new skills available for DL. If none have come out in the 4 years of Oblivion's life with all the extras and wonderful tools available to us, there probably won't ever be.

http://www.gamesas.com/index.php?/topic/1111980-wipwipz-lost-skills/ seems to aim towards this.

Yeah, that would be nice. Yesterday I posted a post about how many creative features that a game call FATE has. Not only it has split skills but what i LOVE about that game is that you can't wield a war-hammer if you aren't strong enough. You can't use a strong armor if you don't meet a certain criteria and so forth. The off-limits of items and weapons until a certain point of the game is what makes good rpg gameplay.

You might want to take a look at either http://www.tesnexus.com/downloads/file.php?id=24717 or http://www.tesnexus.com/downloads/file.php?id=15152.