I do kinda what you're talking about. Heat was the biggest improvement for me. I'm thrilled with my propane Dickerson, but there's other options too. Check out Rainer's heat and trailer ideas too. She has it "wired," so to speak.
http://www.tnttt.com/viewtopic.php?f=42&t=55219 My next important thing was the bed. I use a full size memory-foam mattress for the best afternoon naps and overnight sleeps I get all year. Next priority is my solar panel. Keeps my single 12-volt, deep-cycle battery charged all season. I run low-draw LED lights, charge phone and laptop, and run a 12-volt fan in summer. Speaking of fans, I have a Fantastic portable model, and it works great and draws nothing. It makes hot, still afternoons tolerable. I only cook inside in poor weather, and then carefully on low heat so as not to splatter grease and odors all over. I use a portable crapper, and rarely at that. Outhouses and restrooms are usually around where I go in Montana.
If there's one thing I would like to have, which I don't, it would be A/C. However, I don't want it bad enough yet to run a generator to power it, or cut another hole in the trailer to mount it, or give up the wall space for it, and just deal with one more mechanical thing. I find shade, run the fan, and/or take an afternoon drive in the tow vehicle. I like things simple and nearly maintenance-free.
Many on here have added their own insulation, and in hindsight, I might have gone that way. But, I ordered mine "insulated" from the factory and it is working ok so far. Its thin bubble-type rather than heavy-duty stuff. I don't camp much below 20 degrees, and my heater works fine in that. I never had to remove a panel from inside, and the cost was minimal.
So, we likely cross paths since I spend a good amount of time fishing in Montana from late June-October. Missouri around Craig? Dillon area? Missoula waters? Ennis? West? Island Park (ID)? I like hatches, dries, big rivers, and spring creeks.
You'll love a trailer for this. Its perfect for what we're doing. This place gave me the idea, and all the ideas, and is full of ideas for every option you can think of, and a bunch you never would have considered. The links below have fishing pics, trailer pics, and my thread. Have fun with it!