That spot is prime for one little led bulb.
Fiber optic use back in the 70's was way ahead of its time. I bet Delorean approved that one. That could not have been cheap, I remember fiber optic desk lamps in the 80's, they were expensive, like buying a microwave back then.
Did all models get that fiber cable? Would show how important the ash tray was back then when the ash tray lighting was standard but trunk light was optional.