I have been told the reason the driver has swap the bighter light to the other side at night (can't remember which is which) is so they don't dazzle track workers. When I used to commute at around 07:30 in the morning depending on season and sunrise one train would have left bright the next right bright.
I thought it was just about redundancy - they must display one bright light at all times, so having 2 allows one to fail but for the train to remain in service? No bright headlight = train out of service as I recall.
One only has to look down a straight section of line to see that the current specification of headlight is so very much more visible than the yellow end so I can understand why a change has been mooted - I don't recall ever seeing any other train/locomotive in Europe painted with such a warning colour.
In terms of visibility for trackside workers, I think a system with greater interaction with the signalling system would be a much better way of warning of approaching trains than any visual detection - my experience of (agency) lookouts in the past has been rather varied, which is a bit alarming when you rely on these people for your safety!