Just got finished whatching an episode of This Old House where the resident carpenter Tom Silva was espousing the ROT PROOF virtues of PVC planking and moulding ( made from the planking )... From watching them shaping and working it , it looks like it might make a good long term floor , IF ( the qualifier) , there are enough cross braces on the trailer to best support it ... It was said to nail, screw , and hold paint “ beautifully “ , so it might be a good substitute for door and window frames too ... But the phrase “Never Rots” came up more than a few times ... For the little bit of wood we’d use on a trailer , I’m sure it wouldn’t cost but a little more to make it with something more permanent ... or as he said "150 years" ...
It may be worth welding or bolting on a couple extra trailer cross braces just to accommodate the slightly more flexible PVC floor ... but flexibility might be an advantage , as we know the trailer flexes quite a bit on the road ...
I’m still obsessed with the idea that plywood is NOT what we want to use on the floor .... Sure , its waaaay better than the POS "Oatmeal board" the RV people use ... but still not something that would express the
care free nature of the ideal Foamie trailer ... Wood works great in a home , just not on a camper , and after seeing Kenneth W’s No wood Foamie , that had already travelled so far, I was really impressed

... Ken proving it could be done and Quite successfully too ...
JMHO ... FWIW