That's not a bad idea. I've long been a fan of fail-safe designs. It may get a little complicated though. Might be better to have a very simple and quick way to drop, like a big red button, rather than a timer and all the associated mechanisms. There are things called "explosive bolts" but of course they have their own set of problems. I'm expecting my drop weight mechanism to take several minutes to operate, and I can see how that might be a problem if a very quick release is needed. It operates by hydraulic pressure, and if that fails, has a manual way also. Redundancy is a good thing when your life may be at stake. Here's a sketch but it doesn't show the hydraulics, just the manual device. A small hydraulic cylinder to rotate the drop pin, one small thru-hull for the hydraulic line, and a hand or foot pump inside is all that's missing. Frank D.