Good analysis.
If one was interested in shorting the lower third face due to a high mandibular plane angle and occlusional plane angle, couldn't the person opt to have a genio reduction as in shaving off some of the chin, and doing maxillary impaction (if they have enough upper tooth show when smiling) which would add more CCW rotation and by the forward movement of the maxillary it would show more teeth due to the upper lip, like a cushion, or they could get an upper lip lift to show more upper teeth, right ?
Well, with reference to my observation of the length changes to the lower 3rd, they could take a cross section out of the chin for a length decrease to the chin as opposed to shaving from the bottom. So, the chin could be shortened independently without effecting the rotations done to the maxilla and mandible.
As to adding an impaction in addition to the CCW-r posterior 'drop' to the maxilla, to shorten further, both the bite and the potential aesthetic consequences to the nose would have to be taken into consideration. Impaction is going to cut off part of the nasal spine and they have to balance the bite. So, I can't tell you if an added impaction can be offered just to shorten the lower third more in the absence of any unfavorable aesthetic sequalae. It would depend on whether one's specific measurements allowed for an extra impaction.
ETA: With reference to the top diagrams I Included, it looks like they might have option to lop off a section from the ramus to shorten the lower 1/3rd (in addition to rotating). So, I guess that option could be explored with a doctor (a doctor who performs it?) who told you that you were candidate for Inverted L osteo.