Drill a bunch more holes in the door. Fill door with Great Stuff thru holes. Now you have a vastly improved door which is not only stronger, but also more soundproof.
That would cost more than a new door and might just blow the skin off the door. We need to stay practical here ****ie. And Spurcey wants to cover a hole with a disk with a hole in it, I mean really!
Be sure you live your life, because you are a long time dead.-Scottish Proverb