i understand why it was impossible so far. but with newer features like pop up footnotes - epub 3.0 - it should be real.
i read a book in some device, click on a footnote inside a table and see a pop up window with footnote details -- what can be easier to imagine?
no layout obstacles, that is important.
Thanks for giving us this direction, i would surely escalate your request further.
Hope we could serve you as easy experience possible.
thanks for being excited by this idea. hope one day we will see it in action.