I've been focused on insulating the trailer and the end is in sight.
As I'm planning on mostly boondocking in the mountains and deserts of the southwest, I've got to make this thing habitable in extremes of heat and cold with no option for plugging in to grid electricity. That means no A/C and no traditional RV gas heater.
So I need to insulate it well. In a perfect world, my body heat will be enough to keep it survivable through a cold night. What do I mean by survivable? If I can keep the interior air temperature above freezing on a 0*F night, I'll be happy.
My strategy for summer is to have fans, excellent roof insulation, a good outside shade hang-out area, and the ability to simply weigh anchor and move to higher elevations if it gets too unbearable. I'll consider small, portable swamp coolers, but most of the ones I've seen seem pretty poorly made. (It's important to note that I'm planning on being in warm humid climates approximately never. The design decisions I'm making are very much driven by an arid-only assumption.)