This is NOT a tutorial, although I'm planning to write one, if you're interested. Just ask.
You already know my character Cornelia. To add some background, I'll tell you that she's a Warrior by birthsign, Knight by class, fighters guild Apprentice and, most importantly, the faithful companion that for many years has been facing the dangers of Tamriel by my side. Just recently I took the habit of using Cornelia as player character.
It's been a pleasure following in her footsteps (and in the meanwhile, staring at her nice, firm butt)...
forgive a dirty old man who lives in its fantasies.
Kendo2, are you listening? I have already addressed to you my apologies for the 'incident', both in the public forum and by PM... Honestly, I can't do more than this. It would be nice to hear from you that it's all settled. At any rate...
When I first included the LAPF framework and some of its children mods in my setup, it had to reconsider Cornelia's roleplay entirely. A stainless Knight with 0 infamy doesn't mix too well with LAPF, particularly when you install Bravil Underground and Lovers Slave Trader. I had to convince her to step down from her adamantine pedestal and get her hands dirty.
I've been hunting down half the LL community to teach her how to masturbate like a man (the poor girl didn't object, she's a real darling). Sorry, I got carried away from the subject.
I'm only beginning to explore the potential of Blockhead OBSE plugin, and even though I'm just moving my first steps using it, I'm really impressed. ShadeMe is a genius... but you already know that. The idea of changing Cornelia's gender didn't come to me all of a sudden. It grew slowly around a few concepts I had noticed while using LAPF:
1. The framework provides the means to play female characters as futanari.
2. Setbody and LoversJoystick allow to set an arbitrary futa mesh (can be an animated dildo/strapon/penis)
3. The subtitles provided by AdultPlayPlus are not always in sync with the 'situations' that may arise.
4. LAPF cum settings: spunk textures can be either disabled for female characters, or allowed without exceptions. This leads to odd results like ejaculating from a strapon (well, I'm aware that some specific models make it possible. I always try to keep informed about the advancements in the field). 
5. There are mods hosted on LL that introduce transgender/femboy characters, overhauling the female gender.
Finally, I took the time to read Blockhead's Readme. That really opened realms to my imagination.
I had to pester again the same, patient people that more than once have helped me recently. This blog entry is also the occasion to give them credit for their support and kindness. movomo, are you listening? Thanks.
My first attempt was a partial success. Thanks to Blockhead, I managed to set my preferred female body meshes for a male NPC. In the meantime I had learned from fejeena that the 'skin' material property refuses to accept any texture different from footmale.dds (for males) and footfemale.dds (for females). Changing the name to 'default' or 'whatever' ("disabling the shaders" as movomo would say) you can apply to the body meshes any texture you want. While undoubtely useful, this trick had me sidetracked a bit (it would have been better to use Blockhead also for the texture replacement).
[EDIT]
I thought it might be useful to include the following, detailed description of the material properties. It's a quote from movomo
Certain material property names and NiTri names are hardcoded. A material name of 'skin' enables the skin shader [...] For the skin-ish materials, (bodypart):<> name convention is used to fetch the appropriate texture for the model.
For example, foot(fe)male.dds is used if the model's name is foot:something, because that texture is assigned as the foot texture in the race record. Likewise upperbody(fe)male.dds for the upperbody:something, leg(fe)male.dds for the lowerbody:something, hand(fe)male.dds for the hand:something.
If only I had knew before!
In the CSE, unchecking the 'Female' checkbox causes the face to deform and the textures being darkened. Pasting back the original face (I suggest keeping a "face library.esp" to import face data from your preferred characters, using Wrye Bash) restores the female appearance (not exactly 100% match, it's can be 80-95% based on how you set the age and complexion sliders when the character was first created).
The inacceptable neck seam was the only obstacle left. It originated from the aforementioned 'trick', as apparently I had no way of setting the texture overrides with Blockhead. I mean, usually male textures are in a single file, while female textures have a separate file for the hands. I was about to give up, but then... the missing piece of the puzzle came out.
I had it in my pocket. According to Blockhead Readme, these are the valid BodyPart names:
UpperBody
LowerBody
Hand
Foot
Tail
They're used to specify both the meshes and textures overrides.
In the end, I only needed 3 copies of footfemale.dds and 3 copies of footfemale_n.dds, and have them renamed as:
Racename_Upperbody.dds, Racename_Upperbody_n.dds
Racename_LowerBody.dds, Racename_LowerBody_n.dds
Racename_Foot.dds, Racename_Foot_n.dds
femalehand.dds and femalehand_n.dds became:
Racename_Hand.dds, Racename_Hand_n.dds
I was eager to test the results in game. Screenshots:



The first screenshot shows what's left of the neck seam. It's still visible, but far less than before. In the second you can see Cornelia's (Cornelius' ?) new 'assets'. What are you thinking? I'm of corse referring to the shiny steel armor composed by mixed stuff from Apachii Goddess Store, ANB Micro Bikini (resized to Manga upperbody) and standard issued steel boots and gauntlets. They look shiny just because of the APPLY_HIGHLIGHT diffuse method set in Nifskope.
So, you read this document until the end... I'm impressed.
Happy modding.