Only changes I might make to it:
Spend an extra couple hundred and make the toilet itself as a little room off the cabin, maybe to the side of the back door. Gives you more room on the ground floor.
Don't line up the front and back doors. Better for ventilation and not having your stuff blowing everywhere. Offsetting the back door means you have space for a decent stove and can run the pipe straight up to heat the bedroom.
Storm stays in the tops of the corner posts and well planted retainers in the ground if needed. You wouldn't need the cables all the time, they can be looped and hung on the wall or stashed under the porch when not needed.
Neat idea though!
I own about 230 acres of off-grid timbered property in northern Wisconsin. I just had several timber companies look at a controlled harvest of the timber. It has about 70% maple, some furniture grade cherry and oak. About 10 years ago, I purchased the final 40 acre piece and it has a 12x16 building that an old bachelor built in the 30's from poles he cut from the woods. In its case, it is located in a beautiful, mature stand of Norway pine. It is square, solid and plumb. I renovated it into a bunk house. I have propane heat (might add wood) and I built a loft that has 4 single beds. Downstairs I added a very nice, classy futon that opens to a double bed. The stairs start against one wall and head up towards the peak on the next wall. I added a dormer off the one roof for more light and standing room. I also have an encased, hand-pump well. It is very similar to this in the picture but without the solar stuff and porch. Outdoor privy.
I love it. It could easily be adapted to an off-grid home.
I also have a two bedroom cabin on the next 40 with a pump house (water tank in attic), kitchen (with gas refrigerator) and bathroom.
I am a north woods boy at heart.