I reviewed your website on facial exercises. In my opinion there is not any exercise that can improve platysmal banding in the neck. As we age the fibrous connection between the medial aspect of the two muscle bellies, one on each side, loosens and the muscle bellies separate and descend in the neck n along with the skin which has lost its elasticity. Exercising the muscles cannot improve the degradation of this fibrous attachment. Having said that I don’t think the exercises would hurt either.
Regarding your specific case, I always bind the medial platysmal muscles together, platysmaplasty, at the same time as liposuction, even in young patients. I have found that the results are better for neck contouring even in patients with good skin tone. Depending on how redundant your neck skin is you may benefit from that additional procedure alone or you may also require a lower facelift you reposition the redundant skin and tighten the deeper muscular layer.
I hope you find this helpful. If we can be of any personal assistance we would love to hear from you.