Just bear in mind that there's nowhere to go, if things do not go great. In other words, if I go out en femme in an unfamiliar city and run into massive intolerance (hasn't happened yet), I could immediately return to my hotel and it would be as if nothing happened. On a ship you may not have that option. If you are very comfortable being out en femme in public, and you don't think your presence on the ship en femme would be unreasonably disruptive, then go for it. If not, I might suggest thinking twice....
Just my deux centimes...