Structural systems are a significant contributor to buildings’ embodied carbon and reusing structural elements in new load-bearing applications is one strategy to reduce this impact. However, integrating this approach into existing design workflows without affecting design freedom is challenging. New computational tools like Phoenix3D, a plugin for Grasshopper within the Rhino3D environment, are intended to help master this task. This paper extends current research developments of Phoenix3D by integrating the tool into a more flexible multi-objective optimization framework. Hence, the outcomes obtained from Phoenix3D are employed as an objective function in the optimization workflow. This enables designers to move from a mere assignment operation on a predetermined structural system to a more comprehensive approach, wherein alternative design options are thoroughly investigated. Two case studies are conducted here to showcase this extension’s effectiveness: (1) a theoretical study that compares generated designs with established typologies; and (2) a real-world application of the proposed tool to design a façade system using only reclaimed steel elements. Results show that adequate design solutions are found in real-time and interactively for the same stock of reused structural elements. Not only does Phoenix3D turn component reuse constraints into new circular design opportunities, but it also reduces the detrimental environmental impact of a structure and therefore allows the establishment of a more sustainable building culture.