[monolith]

It's beautiful, I wouldn't hesitate at all to build a bed out of that.
Rough cut a few of the planks- lay them down the middle to see if you like the look, maybe. If you go with the planks, you can always get one of those plastic hallway carpet protectors to roll out to protect the bed- might be less cumbersome and damaging to the finish than sliding a hunk of plywood in and out.