Thoughts on this trailer (project)?

Have you thought about using the axles, coupler, and jack and make new trailer? You could build it to your specs then. This trailer looks very heavy for a 10k gross.

 

I would go for steel channels.

 

Those channels appear to be metal studs. Using them in the flat position is where they are the weakest, they will dent quickly.

 

Wood deck, those cross supports do not look very substantial for an equipment trailer of 10K load, particularly compared to my own 16' + dovetail 5ton unit. My trailer by itself weights in at 2000# . my out side frame is 6" deep C channel 1/4" wall cross supports are about 3/16 thick channel 6". Last week F250 on trailer + f250 tow unit on the scales at 17500 #. F250 6.0 diesel hardly knew it was back there. 15.5 mpg avg. - not bad. That was about a max load rating wise for the trailer.
From the picture more like a 7k unit at max. maybe less. All the decks get a bit slippery in poor weather- Mesh decks- no thank you, the mesh stretches easily and breaks loose at the weld points ( real pia to repair) plus it costs more than a wood deck, every dang thing in the world gets caught on it or tears through it . Wood deck reasonably easy to repair- stiff broom or the hose / pressure washer to clean off.
Metal decks are mostly to thin suffer denting and stretching like mesh with out the grabbing problems- Course it depends somewhat on the amount of supports under it.