Given that there are already small holes through the fiberglass but no 12v lines, I would use a solar light
there. Small panel on the outside running two fine wires to the light and lithium battery
inside. You can easily setup a light fixture with a light that runs on USB and a USB lithium battery
to keep it plug and play simple. Lots of small solar
panels come in USB 5v too. It would be dead easy to setup and you would have a light that runs all nigh for free!
Custom panel batts and charge controllers could be done too, but the USB approach would be cheap and easy if you are not comfortable with electronics.