With regard to the knife situation, may I recommend switching from a knife to some form of line cutter instead. A Z-knife or trauma shears will not be a problem for the ship security check and local island authorities and is a better solution for cutting entanglements underwater anyway (i.e. you can’t stab or cut yourself while trying to cut away that fishing line). I suggest switching to one of these for all your diving, not just from a cruise ship.
I also recommend taking your own regulators and gauges/computers if you have them. To me, it’s worth the extra luggage space to have something familiar keeping me alive. Even if the ship’s gear is new and in good shape, its still not the familiar gear you already know and trust.