There was talk of doing that with parameters that would change the model/texture after loading them, changing such things as size shape, colors, and textures.
Not an easy task, though, as it involves adding additional info to the meshes to accept these changes on the fly. An extremely complex rigging could do this, in effect, creating a second skeleton just for changing the shape of the mesh, rather than making it move. Basic 'poses' would change the model between fat, thin, tall, short, and muscular. These body-shape poses would not be changeable once selected. Examples of the edited animations would be: fatwalk, thinwalk, fatidle, thinidle, and such. With the proper tweeking, the same base 'walk' animation could be used for both fat and thin, but the added body ID would change your look.