Genioplasties beyond 4mm have the tendency to look OK in profile and odd in the frontal view. They also tend to deepen the labiomental fold at he expense of natural esthetics. My philosophy is only do a genioplasty to alter the shape of the chin and to make the shape look more normal, not substitute it for putting the mandible in the correct position in the first place. Many surgeons are uncomfortable with very large CCW rotations and add a genioplasty to get added projection, often doing chin procedures on chins that already have great natural shape. I would estimate that of the 150 DJS per year with 2/3 being Class II with some degree of CCW rotations, that I only do 20 genioplasties. Food for thought
What if the person has an obtuse labial mental fold (groove between lip and chin) as the OP has and does not risk an overly acute angle to the LMF with a modest outward and upward advancement yet would be RELIEVED with more projection there and also some shortening? Her complaint seems very consistent with what the sliding genio could do for her and of course, also spare her from revision surgery.
What if the chin has a good shape (is not asymmetrical in its own right) BUT could look better re positioned outward and upward. Are you saying that in your practice you would preclude a patient who wanted their chin moved outwards and upwards 'because' the shape of it was not inherently bad?
I get the general guideline about not using a genio to compensate for mandibular recession but not the admonition against using a genio to selectively address the chin when a chin area, in its own right could be improved with a targeted genio and also spare a person from total bimax revision.