"Accidents can happen to anyone" tends to be the mantra of those who are negligent. Of course, I am not saying you were negligent or making excuses for your buddy, but the connotation of "accidents can happen to anyone" is not helpful to your argument. Most accidents are the result of user error. Yes, gear failures do occur, but sometimes they occur because of user negligence or ignorance in maintaining or using the equipment. Sometimes accidents occur because of gear failure followed by user error in responding to the failure. In your buddy's case, it is possible that the loss of the weight was a user error (I don't know and I'm not calling it that). If it was the result of user error, then complicating the gear to compensate for user error is usually the wrong solution. (Simplifying gear to avoid user error can be a good idea, however.) You want a more secure weight pocket? There are already a number of solutions on the market, but adding a tether does not make the pocket more secure.
I think you misunderstand the response to the tether idea. It's not that people think it can't be done. It seems like a good idea to you, but most posters here don't agree. That's not being negative. That's not ignoring that accidents happen. That's not saying it never happens.
The tether idea is a terrible idea. Ditch or don't ditch, but don't ditch and dangle.