This is tricky stuff because we're trying to influence subtle details very close to the rotation axes for the thighs. I think any morph that changes the shape of this area in a significant way would have to come with it's own set of JCMs on top of the existing ones.

If I started a new figure from scratch, I'd probably make her all smooth and low-poly between the legs for the initial rigging and try to find some smart way of adding all the detail later on. It's a real pain to keep all those polygons under control while making JCMs, and that's with Antonia being fairly low-poly and having rather stylized labia to begin with.

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