Tman,
Just wanted to say hello, and offer some thoughts from another new guy, here.
I am doing a ctt as well, and like you noted, I want to still have the ability to haul. Especially my small motorcycle when I offroad camp. To that end, I am in a similar situation in that I need to use some level of build, to figure out a lot of the little details of where I want to go. A specific case for me is that I know I want to use my buddy heater for the occasional heating, at this point. And yes, I am aware of the need for venting, not using while sleeping, etc. I have a decade of use with them, so I know the requirements. For the heater, I know I will want plumbing in the wall that will allow a hook to propane on the outside, and a short run of proper line on the inside. The issue is that I am not sure where the heater wants to be on the inside. I am going to need a trip or two of use to sort that out, before installing hardware. I think the plan to go basic, use a bit and plan is pretty solid advice.
As to the electrical, I think the first step is to decide if you need/want ac or dc or both. This site has a wealth of information on ac, but is a bit thin on dc. I also belong to Expedition Portal, and the folks in the 12 volt section can get you squared away on dc wiring/needs. I built a very nice portable solar system last summer, and hours of reading over there got me squared away. The good folks here got me started on ac, and at this point I decided to simply create a waterproof passage way in my floor, so that I can run an ac cord into the trailer, with the doors closed. Using a gfci pigtail (found that info here), and it will work for now. In my case, I have decided to only wire the inside of my trailer for dc, as I have never even been to a real campground. Only remote stuff. If I found myself at a real campground next weekend, my extension cord and floor passage way would certainly work. But, I had already started formulating an ac plan for my trailer, but spending some time inside and really thinking about my needs, decided to go dc.
What I have been doing thus far is spending hours and days reading here and at other forums, you tube etc., pen and paper ready to take notes, and tons of things in my amazon wish list, so as to not be lost to the big time information overload
Craig