I guess I'll admit it -- I interviewed for the then-vacant Deputy Associate Administrator for Civil Aviation Security position back in about 1998. The hardened baggage compartment vault was one of the FAA's showcase projects. There were prototypes undergoing testing at one of their two test facilities -- Atlantic City or Oklahoma City (I forget which one). The intent was that aircraft would have these vaults accessible from the passenger compartment. In theory, if a crew member heard a briefcase going "tick-tick" they could grab it and throw it into the vault where it could detonate safely. The big issue, as I'm sure you can imagine, was weight & volume.