Good luck on your search. Those beautiful ancient cities where built with aesthetics in mind not accessibility. Another thing to be cautious of whether the ship docks in port or weighs anchor and tenders you to shore. This might create additional difficulty for your wife.
All I ask is a tall ship and a star to steer her by; John Masefield
Carnival: Glory 2004, Destiny 2008, Splendor 2009, Freedom 2011, Valor 2012, Dream 2013
Celebrity: Summit 2011
Princess: Ruby 2010, 2014, Caribbean 2013, Coral 2014, Regal 2014
Star Clippers: Royal Clipper 2015