Bulkhead electrical gurus to rescue

I like your thinking.
But the starter is getting power when start position of key goes back to "on" position?
Practically burned my hand disconnecting
Negative on battery(s,) in trunk to stop
With engine not running.....?

Again, nothing has been added or removed
In current system which has been the same for 15+ years.... thats the frustration


And no mods! What is your definition of mods?