Greg, I don't see the point for swapable hips, either. Female equipment does not poke through clothing anyway.
Since I made a V2P2 remap of just the lips and nipples, It should be obvious that my preference is for separate textures there. If I want a transition, I will do it in PP8 or P6.
I have the lips/nips and genitals textures all assigned to their own MAT pose files, so I can switch textures instantly - It is really cool. I also did the rsr's using the textures, so I can see what each looks like. The problem for anyone else is that I renamed the textures - removed spaces and made the numbering consistent. Since it will involve a ton of bandwidth to provide this and I have heard essentially zilch wth that I have provided, what would be thee point?

The morphing is separate from the the remap anyway. But, yes, the texturing is crap without the remapping.
I played with a prop. It is doable. I was thinking about making Millie's genitals material transparent and sticking the prop in the opening.
Actually something like this has been done and is on sale in the store here.
BUT, the author choose to make the prop a part of the hip mesh or alter the geometry of the hip to accomodate it.
My rule is - do not mess with the geometry of the groups.
It messes up too many morphs and messes up the texturing. It causes too many problems.
Besides, a prop, once parented, will stay put no matter what. If you want it to adjust to a spread leg pose, you just do a morph on the prop and slave it to the joint movement.
I am not enough displeased with Millie to get into shaping the prop and doing all the necessary morphs on it. Much work.
What I was going to do, was to cut the keystone area out of Vic's hip, increase the verts where I wanted the extra shaping, set the map and then morph it. I lost interest at the vert increase stage.