Some wiring thoughts...
I like having separate utility 110V circuits, one that runs through the inverter, one that doesn't. My Xantrex 1800w inverter can only pass so much juice through. You want to be able to run the AC/space heater and the coffee machine AND blast the stereo! (BTW: that Xantrex auto-senses whether or not you're connected to shore power, so no extra switch)
I wired in a complete second system for my second AC. Got one of those 50A to twin 30A splitters, and then wired the cable directly into a small panel with a 15A plug attached to it.
Go with stranded wire if you can, not romex. I've had so many problems dealing with the romex!
Wire in an exterior plug near the fresh water fill. Comes in amazingly handy!
I like using terminal strips for the 12V
system- run a fat wire to a central location, install the strip, then do all of your branches from there. Case in point: I recently installed an overhead storage area above the bed. Ran a new circuit up to a terminal strip inside the cabinet, then ran separate wiring from there to the three switched lights and two fans.
Label all of your wiring as you install it, like "to inverter" "from inverter" "refrigerator", etc. Your wiring diagram is excellent, but maybe change it around so that it corresponds to actual locations in the trailer. You're probably going to need it when it's dark, you pulled in late to a campground, nothing works, and your flashlight is dead. I call this "writing notes to my future self". Being able to troubleshoot problems fast will take you from tears to toasts in no time!
Leave strings in the wall as you run your wire, so you can pull additional wires in the future.
I like these switches: https://goo.gl/MdRN4J
Drilling a round hole is way easier than drilling a square one.