AR14 is great about making requested changes, but in the meantime you might want to look into the open source image editor "GIMP". It has a lot of great tools for manipulating images, but in particular "Wave Transform" and "Cage Transform" could do what you ask. I mostly use them to 'shift' character's weight around from one foot to the other, turn them very slightly, that kind of thing, but you can fiddle with body proportions too.
I spent five minutes doing a mockup - attached are two images, a straight export from Mannequin and one I used Wave Transform (bust) and Cage Transform (hip region) on. This is a quick proof of concept, you can dial it in and make it look better with more time (or less extreme shifting)
