Hmm... according to this page (right at the end of the page)
http://www.standardista.com/standard...ations-basics/
We should be able to add an xmlns definition to the html tag even for epub2 to make this legal.
Code:
<html xmlns="http://www.w3.org/1999/xhtml"
xmlns:aaa="http://www.w3.org/2005/07/aaa" lang="en">
And then adding an aaa:role="doc-chapter" attribute to the body tag should then be perfectly legal for epub2.
I wonder if that would pass epubcheck then?