As an addendum, I realized that making cloaks and accessories create partcuts was actually the more achievable part of this, so I'll just have to investigate the partcut data in the pacs themselves to figure out how to create custom cuts.
For testing, I was using the cloak on Cantabile (Lahn), since it's not a perm_cloak, and the Owl Horn Rimmed Glasses, again for Lahn. Both were set to a Ruby Floretta lb pac with no mesh. The partcut data of that pac defines a cut for some of the torso and part of one arm.
Cloak was easy, as there is already a CutType for Cloak that has a Relation that will affect Nude. Here, I just added the file references to the Cantabile cloak pacs.
Glasses was a tiny bit more involved (only because I had to modify one line of code to handle an empty Relation). Created a new CutType called GlassCutters with the sole file reference being the Owl Horn Rimmed glasses. Created a Relation called GlassCutters and added Nude to its list of Cuts.
And voila, easily togglable part cuts. I don't think it really clicked for me before how to do this because, prior to this conversation, it was all just bouncing around in my head, so thank you. I'm probably going to end up buying one or two of each accessory type for each of my characters to make use of this.
