My modest proposal for your Catholic advance directive.

"Furthermore, as a faithful Catholic in full communion with Rome, I hereby offer a bounty of $25,000 (in 2005 dollars) for the literal scalp of every self-styled Catholic who proposes to testify in any way whatsoever in favor of the removal of food and water, regardless of how I may be receiving it."

That way you don't have to worry about the views of "Catholic" bioethicists like these guys.