This and other threads cover a lot about the history of P3D's work on Brad (and Antonia). You are actually accomplished at making figures, and I am not. So these threads would probably make more sense to you than they do to me. Eventually, Phantom3D will come along, and give a better explaination than I can.

Phantom3D did not want to create a figure that used extra resources by having  geometry loaded , but not used. He was trying to figure out how to have a base figure without genitals, and add the genitals with a pose file. He did not want to use the method you talk about, because he agrees that that is a waste of resources.

A conforming figure has a lot of problems that he wanted to avoid.

The solution he found isn't built in, it is substituted for the original geometry by an insertion pose file, that replaces the original geometry, and is then welded in place. Cage and others have used similar techniques for some of their work. Now that he can add and remove the genitals, P3D is trying the technique out on some other ideas, like clothing.

It will be interesting to see what he can accomplish, even if in the end it doesn't turn out to be useful to everyone.

lmk

Probably edited for spelling, grammer, punctuation, or typos.