Regarding the actual climatic and environmental stakes, citizens need more than ever to be involved in planning and design processes. Within the perspective of sustainability as a wicked issue, this involvement might come jointly with an enlargement of individual perspectives towards collective visions, including not only humans but largely all living species, through time and space. Within a complex global problematic, we foresee that the usual problem and solution co-design process proposed is no longer adequate. Therefore, through this paper, we propose the foundations for a new co-design approach favourable to the design of a common interest through the development of a territorial ethic. As a preliminary step before gathering stakeholders in the context of complex problems, we propose a methodological approach of investigation based on multi-sited ethnography that supports a work of wicked problem identification and analysis. Finally, through a case study in the remote mountain territory of Matheysine, we present the result of our investigation and the identification of local wicked issues.