Sustainability and circularity must be integral components of the Product-Service-System (PSS) life cycle development, regarded as essential considerations for every new product rather than optional features. This necessitates the inclusion of goals, documents, metrics, and means in the industrial tool chain, facilitating their seamless implementation. The rapid adoption of "Model-Based Systems Engineering" (MBSE) in companies, supporting the development of updated industrial platforms for system design, positions this methodology to aid in eco and circular design activities. The initial step of MBSE involves an investigation of the customer's or client's needs, along with other relevant constraints, translated into technical requirements [1]. We argue for the necessity of introducing the environment as a crucial stakeholder to assess the system's impacts, thus creating a set of "Sustainability-oriented" requirements. Subsequent design phases include the targeted allocation of each requirement to specific functions or multiple functions to be performed by the system. This allocation involves analyses of increasing complexity, including the creation of numerical models spanning multiple physical domains and different levels of complexity. This process aligns with the definition of Key Performance Indicators (KPIs) to evaluate the performances of each design solution across various aspects (innovation, customer needs, technical constraints, etc.). While KPIs for technical constraints can be easily defined, establishing KPIs for environmental impact remains an ongoing research challenge. Moreover, requirements from different sources may be competitive rather than synergistic. While literature provides strategies for prioritizing sustainability-based requirements, there is currently no strategy for prioritizing sustainability-based requirements alongside conventional ones. This work aims to address this gap, offering a Multi-Criteria Decision-Making strategy to assist designers. The study will illustrate this approach using the design of a velomobile from a circular perspective as a case study.