Unfortunately, I haven't been able to find any place where you can purchase DRM-free e-books, so I think this would require working with Japanese book publishers. The one exception is the Harry Potter books, which are published DRM-free through their own website. I read the first two Harry Potter books using clippings to generate flashcards for each chapter as I went along, and it was incredibly helpful.
The idea of audiovisual context is interesting. Could you tell me more about what you have in mind? I've thought about adding text-to-speech options on the dictionary entries and in flashcards. But something more complete, like what Rosetta Stone does, seems a lot harder, just from the perspective of acquiring rights to the images.