Recall how Sir James Dyson threw a bunch of smaller cyclonic tunnels into a chamber and called it a vacuum cleaner? Well, how about shorter hoppers that run down each side of the trailer? Can't dump out the back though, rather the sides, but at least could load it by hand. Or, a walking floor that is powered by the trailer wheels. Engage the drive mechanism against a tyre, drive the truck/ute forward and as the trailer wheels turn the walking floor dumps the firewood out the back. I bought a loadhandler years ago and that is very surprisingly really good for emptying the tray of the ute.