This mod provides the intermediate outfits to allow you to peel your Serana (or Valerica, since he meshaes are the same) in several stages. She will first remove her cape (which she can also wear on its own), then her belt with the assocuated drapery, then the leather corset and bracers, and the pants. This leaves her just wearing the shirt, and you can supply underwear from another mod if you want further stages.
Serana's cape was separated as two additional armors - One includes the body mesh (UNP) and the other does not, using slot 44 instead.
When the cape is removed from the mesh, there are gaps at the back in both the armour and skin pieces. These were filled in, and the central part of the back re-textured using the laces from the bracer part. This was all possible without meeding any new textures.
Removing the belt and the cloth drape hanging from it left a large gap. That was filled with a new section, and the texture maps were cloned for the shirt part to use the space previously occupied by the cape.
Removing the pants was much simpler, and just needed the body part to be replaced with the full character mesh to make legs available.
The remaining leather parts could have been two separate stages, but I opted for one, as the belt and skirt part had been combined already. This uses a new texture map.