There is something already being developed to manipulate hemesh from what i understand. Its currently in beta testing on a cpl of viewers and is known as deformer. Currently Mesh is created to specificly, most regularly, standard and popular SL shapes, mesh is connected to the bones hence why you cant reposition or adjust size if it rigged. My understanding of the deformer is that it stretches the mesh not only to bone joint but body fat aswell. If its rigged you still wont be able to reposition because of how it links to skeleton but it seems your wish may already be underway to being granted .. at least in part.
I'm no expert, just told how i understand it, i havent really looked into it a great deal as yet but will be doing so soon.