The commitment to a more sustainable world in social and environmental terms requires product design and development (PDD) models that will help achieve this goal. Based on a dialogue between theory and practice, this paper presents the reflections that led to such a sociotechnical model, including its main principles: Ergonomics Quality in Design (EQUID) 4.0. It is grounded on a broad concept of ergonomics and human factors (E/HF), going beyond the traditional, narrow view of E/HF in PDD. EQUID 2.0 included the organisational dimension in the design process but left its role only in the immediate sphere of product design. EQUID 4.0 recognises that E/HF quality in the design process depends on a higher level, i.e. the organisation itself and integrates the contributions of preceding versions in an expanded E/HF concept: one that proposes that E/HF should always include not just the social but also the environmental dimension of sustainability.