Johny,
I was just thinking this For the bed platform. Put some of the oil stuff to protect the wood. Then I would wrap the top with marine vinyl found very cheap at any fabric store.
the vinyl is a million times easier to clean and won’t keep dust like a carpet material. Very easy to wipe down. The added bonus is that the vinyl prevents stuff from sliding around. Finally, since it is marine vinyl it is very resistant to weather.
you could always put a piece of carpet above that if u wanted but I would buy the cheap 24”x24” squares of gym/garage flooring they sell at harbor freight. They would provide a nice cushion to sleep, you could glue them,Velcro them down or just place them down and be able to remove if you want.
Anyway, this was one of the layouts I did on my f250 bed and the kids loved sleeping on it. Just a thought.