Great idea! So do you feel the ground "keep alive" would trip a breaker, or blow a fuse, if a short occurred, or if the starter was cranked (without the switch turned on) as well as the positive wired set up would?

For some reason I keep thinking that a smaller gauge ground wire (keep alive), even fused with a low amp fuse/breaker, would still allow enough of a ground to crank the engine, or allow a short to occur, where as the positive cable would not. I don't know why this is stuck in my head. Am I totally wrong about this concern? I think I am, just want confirmation from someone who knows more than me about 12v electrical systems..

What of my concerns re the alternator/regulator, if one switched off while the engine was running?

I read one comment on another forum that said, "regardless of the switch wiring at the switch, (- or +), the engine would not stop running unless the alternator exciter wire was also disconnected"..I don't know what to think of that..but I seem to recall that a vehicle can continue to run, with battery disconnected. Perhaps this is where I heard of the alternator/regulator issues occurring. If that is the case how is the master switch a benefit at a race track. Car hits the wall, throttle stuck wide open, driver unconscious, track Marshall turns off the master switch, engine keeps screaming..I don't get it? I suppose the fuel pump would be switched off, so that would be a plus, as well as other electrics, that might short and cause a fire..

I suppose in an emergency, where the driver is still aware, you would turn off the ignition switch, then turn off the master switch..