The shepherd's hut is a very simple affair if you go traditional. No frills, little insulation if any...minimal windows and simple siding...usually galvanized corrugated steel.
These carts were meant to be used in the fields in England. It was good to be near the flock when they were lambing...catch birth problems, scare off predators...and they were meant to be hauled from field to field, dirt roads, not on the highways. Construction is super light, much like gypsy vardos,(caravans) diagonal bracing was from the broad rectangular pieces of siding. Many were not braced diagonally at all, and some still are not, with clapboards nailed directly to the spindly studs, and narrow plank interiors.
These days, they have wandered from the true and original form. They can be very luxurious.
Similarly, you can make them look very traditional for the romance, or you can make them as practical and luxurious as you like. Just because I have chosen to make the outside as much like the originals as possible because I like the romantic look, you could do this on a trailer instead of the iron wheels and it could be just as mobile as you like, carpet(YUK) if you like, beautiful stained glass, kitchens, baths, lovely furniture and fabrics.
My departures will be: cork flooring, a beautiful raised panel cupboard bed, antique stained glass in the door, a compact kitchen, and composting toilet and shower combo....my best MINI-furniture and a video set-up.
Here are some pictures from Wikipedia of gypsy Vardos.
They are absolutely glorious, but I know I could never keep it up properly.
I include a couple of images of Shepherd's huts from a private website. I hope they will forgive me as I include their website. I will try to add a couple of other web addresses.
Other good sites include:
I am sure a little searching will find more.