I think this stuff would work great except for the thickness, which is 1-1/4 inches. If you can rip it down to a thinner piece, it may be ideal, maybe even better than wood with regards to durability.
I finally did my week-long fall
camping trip and we used the shower almost every night. The slat floor worked perfectly. I removed it for showering and put it back in after everyone was done showering, which gave us a dry floor to stand on later but still allowed the floor to dry out during the night. I'm very happy with this addition so far.