You can build a bike out of a commercially available bike extension cargo rack.
Normally this cargo rack mounts behind a standard bike to extent the back wheel 1.5 feet back and makes room for its own large panniers, it has a a wood deck on top and plenty of tie down points for heavy duty hauling.
This project is about minimizing the bike and having a compact "sport hauler" where the rider and passengers all sit on the rack. The rack is the only seat, but(t) it's big enough for a couple of people.
The other two bikes can be seen on my hobby website woodenbikes.com