I was trying out something like that for Fallout 3, and from what I found out after a little tinkering with GECK, is that with the Animated Prostitution mod, you already have a solid groundwork for the animation side of things. Where most of the work will be is the dialog, quest, scripts and storyline. I don't think the main story for this game is suitable for a mod in either Fallout or Oblivion.
That being said, I'd like for there to be some kind of tier system for this mod. It should be easier to make someone like Silver or Nova, who had/ is already doing it whore for you rather then someone like, say, Sarah Lyod.
Good thing there are already alot of custom clothings in both games already. It shouldn't be too hard to make/remake certain characters for the game. The hard/ tedious part would be to combine them all into a whole.
For inspiration, there is also the wasteland player mod. Too bad it was discontiuned.
For main storyline, it could go something like this;
You are wandering the wasteland when you came across this broken down house in the middle of nowhere. Thinking of a chance for some loot, you break into the house, only to find a withered man locked alone in a cell. He is dying, staved nearly to dead. He is too weak to move, but his eyes was burning with need and vengence. He spoke, telling you of how he came to be in this state.
This place was once the primer brotel in the wastelands, and he the proud owner of said place, as well as a stable of girls that he had broken, and then used to build the place up. This happy state of things lasted until he 'aquired' a certain girl, one that was fresh, and not already worn down by the hash wastelands. She was captured not far from the settlement of Megaton, and claims to come from the Vault near it.
He set to breaking this new girl, excited by the prospect of taming a vult girl. However, she proved too strong, and managed to not only escape herself, but also sparked a revolution from his stable. The girls, drunk with freedom, rampaged through the store, killing the customers and very nearly himself too. Only the need for revenge stay their hands, and they imprison him in the very cells he used to keep them, and left him to die there.
He managed to survive for a year, a long year of stavation broken by the rare rat or roach, with only his rage and thoughts of vengence to keep him alive. In the end it nearly wasn't enough, but he had survived long enough to pass on his will. You are chosen for his revenge.
You sat by him as he died, too late for anything you could do to help. But now you have a choice. This man has left behind tools and equipments for his trade, things even the slavers of Paradise Fall has never seen before. Drugs and formules for subduing girls. A secure location. You can choose to do the right thing, and torch this place to the ground, or you could carry on the work of this man whose name you don't even know.
The choice is clear...
Being good is far too overated anyway...