I just started learning how to use Google Sketchup so this is terrible but it gives an idea
In the interest of simplicity, we've chosen a shed roof...but may end up making it complex anyway by making it a vegetated roof (aka green roof). A vegetated roof would greatly increase the life of the roof waterproofing (possibly indefinitely) but its, as said, more complex and its more expensive. On top of that, I the builder/architect/engineer need to be mindful of the additional roof load (especially when wet) and build suitable support for it.
Another possibly stupid complex idea I had was to use a staggered stud arrangement. Picture explains below:
This method is a compromise between traditional 2x4 stud construction and 2x6 "advanced framing" construction with the added benefit of reducing thermal bridging; you'll notice that none of the studs extend from the outside to the inside, there is always a gap that can then be filled with insulation greatly increasing the performance. The cost is of course using more 2x4s than traditionally and some added general complexity, especially for openings like doors and windows. Id space the studs every 12" on center on the stagger which would be every 24" on the interior/exterior. Another plus is all this lumber would surely support even the heaviest roof loads.
Our little Sketchup drawing shows a rough layout of what we'd like, small kitchen area, micro bathroom with composting toilet, sleeping loft and a small seating area.
We'd like to maximize solar heat in the winter so we're putting a big glass double door and a big window on the south side.
All of this is incredibly rough, nothing set in stone yet, but at least some direction to march forward in.