I came across an earlier post on the net which mentioned getting a version of XHTML 1.2.
I think this is an excellent idea as there are still presentational attributes present in XHTML 1.1.
I've added a list of what I see these to be in a feature request for Tidy: https://sourceforge.net/tracker/?func=detail&atid=390966&aid=1763528&group_id=27659
