Sounds promising—earth can give great insulation and protection, but you’ll want to check the slope and drainage first. Maybe build a low berm behind a timber frame and let the soil tuck in there; it’ll add mass without killing airflow. I can sketch a quick plan and we’ll tweak the angles to keep the rain out. If you want to test it out, I’ll bring my measuring tape and a few stakes—just don’t let the earth get all toasty on my end!