I had trouble laying the skirt on and yes the draping was difficult for me, too. The way it came together in the back was just a big mess - hence the bustle. Modeling the black body part was hard - I kept making it too big/fat and having to start over. I do a lot of figure modeling, but they usually don't have form fitting clothes. Getting her boobs just right turned out to be more trouble than I expected. The only think that was easy was the necklace because I have a mold for that.
Perhaps if I'd planned it out and had come up with a better method for cutting out the skirt, I'd have had an easier time. Oh, and you have to cut out her top, too. That looks super simple, but it wasn't for me. I eyeballed it and cut out the right shape pretty quickly with a little trial and error. But that's just not how i like to do things. I absolutely despise having to do something twice.
Now that I relived all that, i think I'd raise the price by another $100 lol
The draping was a good design though, because that way I didn't have to worry about any texture problems on the top half of the skirt, which you can see they had on the one in your picture. The ganache should take care of that problem though.
It will taste a whole bunch better the way you're planning to do it, but it sounds really hard to me. But I hate working in rkt and only use it for very simple shapes.
Good luck! I'm sure it will turn out good since you're thinking it out. I barely gave it a thought and assumed it was be extremely simple.