I'm not quite sure I'm exactly following what you're proposing in terms of enclosed and non-enclosed space. However, it doesn't seem like a good idea to me to live in an RV in a fully enclosed building in the wintertime if you have a gas furnace or water heater running. In a house, of course, there's a chimney or other vents for the combustion gasses from such appliances, but you'd be essentially venting your RV to the indoors. This would at the very least lead to a lot of moisture in the air (and condensation in your building), and quite possibly to carbon monoxide accumulation if the combustion isn't perfect.
I wonder how much time and money you'd be saving by building a large barn of some sort but still installing water and sewer and (solar) electric vs. building the house. I guess maybe it depends on how fancy and large a house you're contemplating. Maybe you could build a small camp/house that can later be easily extended or finished off. It seems to me it may be an option to consider if you haven't done so yet.
Growing up, my family lived in a Banner motorhome for several months—I don't remember exactly how long as I was about four years old at the time—while constructing our log home. We moved in to the house by Christmas, barely, and the house was far from finished at the time. Fun, if somewhat vague, memories...probably more fun in memory than in practice, truth be told.