While Engineered Living Materials (ELMs) are increasingly investigated for technical viability, discussion of their broader societal implications remains limited. To address this gap, we conducted a multidisciplinary co-design workshop centred on a self-healing biomineralised bacterial cellulose (BMBC). Twenty participants from biodesign, bio-nanoscience, materials science, and engineering worked in six groups through a three-phase process: 1) generating application concepts, 2) designing how self-healing would unfold and be experienced, and 3) reflecting on ecological, social, economic, and future implications. Workshop outcomes and discussions were analysed using thematic analysis. Participants framed self-healing not merely as functional repair but as temporal, expressive, and relational transformation, emphasizing personalisation, regeneration, trust, and systemic embedding. The study demonstrates how early, material-led design exploration can surface societal dimensions before technical pathways stabilise. We argue that multidisciplinary co-design supports more responsible ELM development by revealing how such materials may function, be interpreted, and acquire meaning in everyday contexts.