I am tall which is why I suggested recessed lighting. The new LED fixtures are thinner, so there are more options for recessed or surface mounts. You could even use ribbon or rope lights if maximum insulation is the priority.
So, to answer the question about what I did with the hole. On the roof with the opening I cleaned everything up then put a layer of double sided tape down then a solar panel on top. On the inside, i added a piece of plywood to give support just in case anyone stepped on to the panel on the roof and not realized there was a hole there. For the future, I will be adding a "ceiling fan" based off of 120mm computer case fans and a fan controller. I had thought about lighting here as well but focused just on the fans. These fans can be very quite yet move a decent amount of air. My goal was to have some air circulation inside the camper.
Here are some images to clarify things.
