Neat looking stuff, primorge! Way ahead of anything I've tried with keyed dependencies so far.

In the meantime, I had a quick try at doing subd 2 vertex pushing for furrowed brows with the Poser morph tool. That's a resounding nope, LOL. Starting with the fact that the mirror function makes Poser crash, which I think is caused by Antonia's extra brow geometry. But it's also just not responsive enough for any detail work. So Blender and pydeltamesh it is, possibly with some tweaks to the latter to allow me to load just a new subdivision level for an existing morph without baking the new deltas down.

-- I'm not mad at you, just Westphalian.