Having some structure is useful when you don't know what you're looking for, or even what kind of thing you're looking for. And I find that's true of a lot of the technical documents I read. I also quite enjoy reading a physical book with a dozen bookmarks and fingers, being able to see several full pages of text at once.
I could see your way of doing things being useful, though. I suspect it hasn't been partly because it's harder than it sounds (look at the design process for HTML, and all of the mistakes that were made and alternatives that were proposed) and partly because so much of the relevant IP (and thus market) is already locked up pretty tightly.
I agree about the structure. The thing about most technical, or how to call them, non-literary? books is that clearly you are not expected to read everything. In a sense, you start with the given structure but make the book your own as you go along. You skim, see that you already know about this, that you are not interested in that, and are _very_ interested in that. What I'd like to see is a format that makes it easy and gives us new possibilities to make a book our own. What I didn't see is your second point. Perhaps I imagined it too easy, maybe it is actually a tough nut to crack. After all, the format must accomodate all sorts of books and styles. And the IP issue, oh my...
I could see your way of doing things being useful, though. I suspect it hasn't been partly because it's harder than it sounds (look at the design process for HTML, and all of the mistakes that were made and alternatives that were proposed) and partly because so much of the relevant IP (and thus market) is already locked up pretty tightly.