Asymmetrical Train Bustle?

It's really hard to do this without having the gown in front of me to play with it and see how the fabric drapes while trying different things. But, this is what I would try first - Left the overskirt and bustle the underlayer in the ballroom style. Drop the overskirt back down and lift by the satin band to the place on the left hip where it looks like there are buttons you can use as anchors. Drape the fabric in folds so it models the original design. Place the pick-up points as needed for the drape to fall nicely across the back. 

~Lea