Design principles are widely used in the design field, yet some remain visionary rather than grounded in real-world applications. Assessing their effectiveness is therefore essential before implementation. This study focuses on a set of visionary design principles intended to promote the flexible use of railway station areas: (1) Ensuring event visibility by aligning paths and spaces; (2) Incorporating reconfigurable elements and reconfiguration-supportive layouts; (3) Establishing high-quality connections at different scales; (4) Adopting scattered layouts for high capacity or vibrancy; (5) Prioritizing core spaces for humans instead of vehicles. This study aims to address the gap in validating these design principles. Recognizing the potential of jointly employing research-by-design and agent-based simulation, this study presents a major research question: How effective are these design principles, as demonstrated through research-by-design (RbD) and agent-based simulation (ABS)? Methodologically, it first applies the design principles to Station Xtreme and generates multiple design proposals, then simulates the generated proposals, followed by assessments and reflections. The results suggest that the principles are generally effective, though limitations emerged: for example, quality connections may demand greater investment and space, while scattered layouts can increase wayfinding difficulty and operational complexity. This study contributes to the growing body of design knowledge by validating these flexible-use principles. It also introduces a transferable conceptual framework that integrates RbD and ABS, offering a novel methodological approach for testing other visionary design principles.