Saying the "Silk Road" of anything is kind of dumb. Other then the druggies, no one really likes that aspect of bitcoin here. We profit from them, but the drug addicts don't tend to mine and build payments gateways,etc... This forum, I'd like to think, is more about people trying to make money by propagating a future
With that said, I'm sure it would be easy enough to setup any kind of pirate site to charge bitcoin for downloads/memberships. You'd have to really go over the top though, and appeal to tons of niche crowds. I personally wouldn't pay for anything pirated. I still buy my physical copies of mangas.
The whole point of my idea is to align all the interests and bypass anybody who aren't helpful. Manga are left in the dustbin of history, mangaka can't monetize their work, translators only work part time, and so on. Sure, you and others may buy physical copies of the book but it's a hassle. Plus, some of your money also go to printing operations.