Frankly you are supporting the status quo and the big players who are just not the dominating player.
May I suggest that you look into what I am doing at http://5doc.org. Let’s get rid of software/hadware readers and just use the browser. And suddenly HTML5 developers can now use their dynamic code for offline docs without having to navigate the BISG matrix.
Funny enough while the IDPF and W3C are busy writing specs and changing names (used to be EPUB+WEB, but I am incapable of remembering the new name), I’ve already built a rendering engine with WordPress. I have samples with images, math, SVG, code formatting — that can be edited and viewed in an online page and compiled and downloaded in real time with the click of a button.
I also have samples built using fullpage.js with sections and chapters and I am almost finished with adding reveal.js presentations.
I welcome your feedback.