That is just about what I wound up doing. There were only two transparency maps and six texture maps. So I just did the manual loading of the map files, and created twelve mc6 files to cover all the combinations.

What I had hoped for was to create two mc6 files that would change the transparency without affecting the texture, and then six mc6 files that would change the texture without changing the the transparency. Apparently this is not possible from within Poser.

In the process of researching this topic, I found a web site with a lot of tutorials. It is at https://www.foro3d.com/f337/tutoriales-para-poser-54225.html. The web site is in Spanish, but the tutorials are in English. Good English. One of the tutorials is about "Understanding Poser File with Material Settings." I have downloaded that, and I will try studying it to see if it stimulates any ideas.