Here is an O-gauge approach which is admittedly a much simpler task. OTOH, note many of the dimensions are not at the limits of common parts - 1/16" tubing is not the smallest, 1.0mm fiber is not the smallest, 0805 surface mount LED is not the smallest. Hmmm, illumination being 2-D means the square of the scale ratio (87/48)^2 but then these LEDs are only driven at 5mA so using 20mA compensates with 4x the LED brightness.
I experimented a bit with notching. I didn’t use/need it but discovered if the notch has a rough surface, shine the light into the tip rather than open end of the notch. This seems counter-intuitive but I saw a 2x difference; if you try it, it will make sense right away.
Note the gotcha about sliding the shell over the passenger seats. You may not have this problem if your seats attach to the shell/frame before being attached to the floor.