It's extra hard to make it legal in Germany.
The home I build won't be tiny, but it will also not be a "normal" American monstrosity.
Things I am considering most in my build:
-Natural materials fastened via methods that don't require fasteners. This will extend the life of the structure by over a century or more.
-Direction of build, since I want to incorporate passive solar heating and rejection
-deep overhangs, extending the roof for water collection and possibly more solar
-storage everywhere. There is never enough storage, especially for books.
-The eliminating of nearly all plastic, especially in the water system (this is very difficult/expensive with modern plumbing π)