I can assure you that, upon presenting your car to an SCCA tech inspector for its logbook, one of the very first things the inspector will do is ask you to start the car then he/she will reach over and flip off the master kill switch to see if the car stops. If you're comfortable having someone do this using just the battery circuit, and it works, then you're all set... - GA
[/b]
I understand that. But somehow we're not understanding each other. It's probably me because I didn't stay at a Holiday Inn Express last night.

Based on the diagram in teh first post, the car is wired such that the positive connection of the battery has two leads, one which connects to the alternator (let's call it "wire 1") and one which connects to the ignition system and the rest of the car's electrics ("wire 2").

If the car is running, and the alternator is producing output, that output will be going straight to the battery on wire 1, and then from the battery to the ignition system on wire 2.

If I put a switch in the middle of wire 2, then when that circuit is broken, there will be no voltage on the field circuit, either from the battery or from the alternator, because both the alternator and the battery are upstream of the switch. Further, the alternator isn't left hanging with nothing to absorb its remaining energy, because it can still reach the battery on wire 1. Seems to solve all of the problems. And yet I keep reading between the lines of what you are saying, in which you are implying that either this will not stop the engine, or maybe you're saying that it will stop the engine but will harm the car's alternator or other systems.

What the heck am I missing?