With consistently increasing amounts of transported goods, autonomous cargo transport has gained increasing interest as a potential solution. In addition to reliable autonomous driving functions, Autonomous cargo transport requires a wide range of additional software and hardware components to ensure a safe and efficient transport of cargo as well as a pleasant user experience for the customers. This work presents a general concept for an autonomous and flexible cargo transport system, targeting point-to-point transports in the range of the typical last mile. The proposed concept provides flexibility for demand-responsive passenger transport as a mixed cargo-passenger transport solution. Furthermore, the proposed concept is realized through designing a removable cargo hold with electronic locks, and software modules such as a Booking App, a Scanner App, and a central backend. The implementation was developed, deployed in an autonomous shuttle, and extensively tested in a peri-urban quarter of the Test Area Autonomous Driving Baden-Wurttemberg.