There are lots of reasons not to combine cheek work with jaw surgery:
- Extra procedures create extra risk. This isn't obvious to anyone who isn't a surgeon. Blood clots are no fun.
- Healing and soft tissue changes are unpredictable while cheekbone augmentations are very sensitive to small discrepancies. It's harder to get a good result when they're done at the same time.
- Because not all problems should be fixed. Cheekbone augmentations are problem prone in general.
At 4mm, you're borderline for using an average surgeon. You'll only get 5-7mm to the airway from a standard BSSO leaving you at 9-11mm, normal but still slightly deficient. There's only a few surgeons in the world who can deliver a better result right now to my knowledge. PM me if you want names.
Otherwise, the main thing to look for is that the surgeon does CCW rotations, ANS shaving, and alar cinch.