Now that's dedication. Hope they succeeded. The script review on your site summed it up well. I suspect they may have some ratings troubles if it's a bloody as indicated, however, having seen Hannibal who knows what the standards are any more. The only other juicy bit involved using real hookers for the nude scenes in the opium den stuff.
Prostitution is legal in the Czech republic so they cast the real thing.
It makes sense to have pros who are comfortable with nudity, etc. By all accounts, Depp was great to work with and very dedicated. Coincidentally, I was in London not long ago and went on a Ripper walking tour to see the real locations. For the film, they built the entire East End of London in a lot in a village outside Prague. It was bulldozed after filming was done.