A sort of armor mod that automatically swapped to sexy versions of the army during scenes.

[Lewdci]

I remember binging through the nexus for new armor for Serana when I spotted a mod that edits vanilla armor to have certain parts of their armor stripped away during sex animations. It included not just armor, but also clothing too. Didn't take it then but now I do want it, but for the life of me I can't remember what it was called. All I remember was seeing it on the Nexus. 

[Polyleritae]

It sounds like you're looking for Various States of Undress.