Integrating crops and livestock is an agroecological way of farming as it enables maintaining production levels while limiting negative environmental impacts. At the farm scale, crop–livestock systems declined due to globalized markets, policies, and limited availability of workforce and skills. Exchanges of manure and crops among already specialized farms are one option to overcome these limiting factors but are still underdeveloped in the reality. This study aimed to design reality-based agroecological scenarios of integrated crops and livestock systems within a collective of seven neighboring farmers. We focused on 7 farms in southwestern France already interested in developing exchanges to achieve self-sufficiency in fertilizer and animal-feed inputs. We applied a participatory method involving the collective of farmers and a group facilitator to define the problem and generate scenarios, as codesign increases the potential for adoption among farmers. The scenarios selected were evaluated using a supply–demand balance model and a multi-criteria framework including economic, environmental, and social dimensions. Among the four alternative scenarios evaluated, the selected scenario considered both (i) the insertion of cereal–legume mixtures into crop rotations of arable farms and (ii) transfers of manure from livestock farmers to crop farmers. In this scenario, individual gross margins increased and environmental impacts decreased, but workload, logistical, and social issues, such as knowledge development, increased. Compared to more ambitious scenarios, the trade-offs between individual and collective benefits appeared acceptable and resulted in greater autonomy in decision-making at the collective level. This methodology can be applied in other contexts, in particular with other farm collectives.