Remember the old adage -
"There's nothing in the world heavier than a homebuilt stock trailer"
I think that applies very well to this type trailer too. An already underpowered and overloaded 40 series pulling an overloaded and overbuilt trailer almost guarantees that you will end up needing lots of spare parts, tools and fuel.
My idea is to build a very simple box frame and long tongue, use expanded metal for floor decking, spend real money on good ProTech or Weatherquard truck tool boxes along the sides and over the tongue for your valuables/vulnerables and go from there. Torsion axles are bulletproof and relatively cheap - good tires w/ same bolt pattern would be a neccessity.
Cost: ~$750 in toolboxes, $200 steel, $175 for axles, $??tires/wheels
Main necessities for Nevada are fuel and water - those don't need to be covered just cabled together and locked to the trailer
Won't be as "nice" as storebought but ought to work just as well - spend the rest of the money you saved on parts and vehicle upgrades and you won't need to carry as much stuff. go lightweight with your camp supplies rather than bringing the entire kitchen sink and I think you'd have plenty of room.
Or go to Caravan Tops in Reno and have them start building one - that would probably be alright too.