You might do better to, as mentioned, head for Renderotica and ask if anyone there is building one. Lots of good folks there who make girlie-bits (and, well, boy-bits to fit on girl meshes, etc) that seem to work fairly well for (and often beyond) intended function.

You might be able to kitbash a somewhat functioning bearded clam by using (as a workable base) an existing geografted one built for Genesis3/8, Vicky4, Terai Yuki, or even Vicky 3... as an odd idea, you'd use the Fitting Room to convert the add-on bits, then use a magnet to pull up the interfering pelvic bits, and then cook up a roll-your-own texture that blends in - maybe put on some pubes to cover any stray irreconcilable seams?

I remember a hella long forum discussion on 'rotica (or PoserPros?) about this a long time ago, and that's the best my memory can cough up for suggested DIY solutions. Wish I could be more useful in that regard. Just note that it ain't gonna work as well as one purpose-built for the mesh.

The reason why the ladies arrive, shall we say, incomplete, is 1) DAZ is stationed in Utah, so LDS sensibilities kicked in for the longest time (plus they were marketing their figures to kids for awhile IIRC)... v4 was the first figure that didn't have a barbie-doll pelvis, IIRC, but you still had to get the bits separately? (This getting old crap sucks.)

Other meshmakers followed suit for the most part (plus it saved time in the workflow, etc.) Finally, in the bad old days (and even now), less mesh/tex/complexity = less strain on the render times, so unless your figures were riding the meat train to poundtown, it made no sense to mesh-in a working genital set (male or female).