There are plenty of military-issue quick release vests, including some which, I assume, can be clipped to a tether. Pull the cord/ring and they fall to pieces and fall right off you—no straps remaining around the legs or such. Specifically designed to save your life when you are laden with a hundred pounds or more of gear and fall into the water. So the technology is there. The question is, do you want untrained civilians rooting around in an open-doored aircraft, who can with one inadvertent pull or hook literally launch themselves into space? Not me. Strap 'em in tight and don't let them out of their seats.