Yes mfgrs could do it easily. and retrofit kits could be easily made by the hundreds of millions. But again, it truly is something which would require adoption world-wide through legislation and various transportation safety boards. I think it truly is a glaring omission from the information stream we get in traffic.
I like the idea. Where I live there is an intersection that is about 20 miles north of the next traffic light. It is a 65 mph thoroughfare between small cities with a lot of truck traffic. Heading north, there is a small rise and slight bend before that 1st traffic light, making it suddenly appear.
The traffic light is set to change for vehicles turning onto the highway from the side road. I never, ever make that left until I see traffic slowing. They are traveling faster than the speed limit, which I admittedly do sometimes. I have seen too many trucks run the red light, because they didn’t note the traffic light change soon enough to stop. A front brake light would let me know, they see the red light and are stopping.