Hi,
with the attached patch (quite easy honestly ;)) we can generate an EPUB.

I don't have a real e-book reader to test it on, but I used calibre (and its viewer) and the file is usable, and the cross-reference links works just fine; there are some CSS effects that are not shown (like the color in some boxes, like See also sections and so), but at least we have something to work with :)

What do you think would be the next steps?

Cheers,
Sandro