If I remember well vertices in the 'choreographed' group follow object translations. So if you add the vertices at the place where you want to pick up the skirt to that group you may be able to lift thge skirt there. This method of course does not work for hybrid clothing where the skirt is say the hip actor and you can have only one animated action. You can grab the skirt in 2 locations but then these locations will have to move as one.