On the subject of knives, it seems to me that a good J-hook would work best (and safest) for cutting through the line quickly. As an ex Navy parachute rigger I have found the the J Hook necessary equipment in many situations. Slices through suspension lines, seat belts, and rappelling harnesses with ease.
Additionally, I have reservations about auto actuated PFD''s. They''re great if there''s a good chance you will hit the drink unconscious but otherwise I find them to be more of a safety hazard by themselves than are worth it. If you or crew wear a auto actuated PFD please use caution wearing it below deck. A heeds bottle mounted to the bulkhead is also good piece of mind.
Just my $.02.