deliberately withholding a construction set that they had previously promised to deliver (way back when the game first began its development). You'll eventually see some decent fully nude mods for F3, but it's going to take a little while for the modding community to put a serviceable tool kit together. I know that people like Throttlekitty and some other folks at SourceForge are scrambling to remedy this issue and hopefully, they'll have something definitive soon. As a result, they can not yet be imported directly into NifSkope (a mesh rendering tool). To complicate things even further, Bethslop cleverly decided to develop an entirely new NIF format for the character models in F3. The female body meshes need to be completely re-worked, before you'll see anything even remotely approaching the high-quality nude mods that one can obtain for Oblivion.

but in the end, it's still gonna be a pig. I can slap a spiffy new paint job on a pig. REASON: the models in this game are positively revolting. But in my case, I've put my own mod on hold. I'm sure that quite a few people are working on nude mods for F3.

Fallout 3 naked mod