Might want to tone that back. Even long-time building teams have issues building the infamous 3x4 dirt hut. The nightmares, oh the nightmares.
Perhaps a better start would be a large fortress; not the normal medieval kinds or military base, but something like Jaba the Hut's palace from Star Wars or a flying fortress. Or maybe that's not his thing, and a better idea would be some big mining facility that has tunnels deep within the world. Perhaps that is too challenging, and creating the perfect medieval house will start a big Renaissance town build.