The engineering rationale, composed of established logic for the design and development of products, has been confronted by a shift to a circular economy. Digitalization (e.g., Industry 4.0) enables transformation, but it also increases relational complexities in scope and number. In Product–Service Systems (PSSs), the combination of manufactured goods and services should be delivered in new business models based on value-adding digital assistance. From a systems science view, such combinations cannot be managed by the same approach as if they were one uniform system; rather, it is an interdependent mix of technical, social, and digital designs. This paper initializes an updated conceptual discourse on PSSs and provides a reflection on the expected challenges in the transformation from linear to circular models. For example, the role of systems thinking to guide early design stages is discussed and the importance of processes for creating shared visions at different systems levels is suggested to be addressed in future research. The intention is to formulate thoughts about radical cognitive changes in order to realize the PSS paradigm.