I do agree with you that more people in the cab is "better", but not long ago THREE people in the cab missed a red signal and caused a head-on crash.
I have thought that maybe a lineside device might help... such as a "gate", similar to a highway crossing gate, that drops across the track... maybe flimsy, but of a material that would make enough noise in the train to attract attention. I know that in some countries on some lines the trains have to actually stop and move a gate manually, but I am thinking of an automated system that works in conjuction with the lights to present a physical barrier (however easily overcome) to the passage of the train.
Maybe even a device that would warn any oncomming traffic of the opposing train having passed the signal/barrier.