The two wrinkle maps have been redone, with “stretched” versions of the high detail static bump/displacement map incorporated into them. The masked portion of the wrinkle map now dissolves into the static map instead of adding on top, to create the impression of stretching pores/microstructure.
I leveraged this for the sculpted soft tissue detail as well by baking the sculpt and adding it to the static map instead of using Multires directly. Not only does this save memory, it allows the lips in particular to change out of their sculpted shape when stretching.
Now all I need is a way to have a third map activate only when two controls are moved together, so I can add dedicated “worry” wrinkles along with some other missing wrinkles/distortions.