After reading some of the posts here, I'm wondering if these protective devices exist?
(1) open-neutral detector in the main panel -- to detect open neutral before the main panel for two-phase panel and should cut off the two hots immediately when this condition is detected.
(2) ground current monitor/alarm -- the ground wires are normally not supposed to carry any current. So why not put an amp meter on the ground wire in the main panel and sound an alarm if a current is detected? You would need to separate the ground bar from the neutral bar and connect them with an amp meter.