Seagal's designs are fantastic. His approach is more convincing in terms of fab methods/cost and looks a little less standardised compared to wikihouse imo.
His approach is pretty well proven in that some of the buildings have been standing over 40 years which seems long enough to find most of the issues. Insulation/sealing and permitting are the two I know about, at least at house scale, but If I needed a temporary storage shed it would be a great way to build & be able to dismantle later.