Electrical, mount a new fixture.
I took a fluorescent light down over my medicine cabinet because I could no longer get a bulb for it. The wiring was loose in the wall and the box is covered with drywall. If I remove the drywall and open the box, take the wires off running out from the bottom, put a plug in the bottom knock out, and then mount the fixture on the box with a bracket if needed, and fix the hole in the wall they put for the wires, so it was centered over the mirror. I pulled the medicine cabinet. This seems like the best way even though my wife said the light would be better centered over the mirror. I was thinking of replacing the cabinet sometime. I would be satisfied with having the right amount of light and a functional bathroom. All the information I have gotten suggests the best way is to mount the light on the an octagon fixture box. This would mean replacing the fixture box which currently is square.
