The early design phase of complex, capital-intensive systems is critical for shaping their architecture and value proposition. However, such systems face numerous challenges from technological, economic, market, and regulatory domains. In addition, considering system-of-systems introduces new hurdles as the focus shifts from measuring performance to assessing overall effectiveness. Together with the growing trend of servitization, where traditional products are combined with value-added services to deliver functions, a lot of uncertainty is introduced during design decision-making. To handle these uncertainties, systems engineering literature advocates for incorporating lifecycle properties into the system that enable the system to deal with these uncertainties once deployed. Systems that consistently meet evolving stakeholder expectations, despite the changing contexts, are called value-robust systems. Changeability is one such property that allows the system to achieve value robustness by changing internally in response to changes externally. During the design stages, the goal is to identify and integrate options that would enable the system to exercise change and sustain value under all conditions.

In this light, this thesis aims to support the integration of changeability in complex systems by facilitating its assessment during the early design stages. To achieve this goal, it first identifies the existing methods and challenges in changeability assessment for achieving value robustness. To address these challenges, it proposes the Changeability Assessment in Systems during Early Design (CASED) method, which supports development teams in creating value-robust systems in the face of uncertainty. CASED is one of the core contributions of this work, allowing a holistic consideration of identification, quantification, and valuation of changeability during early design stages. It maps the expected mean value and expected standard deviation for each design as a function of changeability level, which serves as a guide for decisions concerning changeability. Additionally, this thesis explores the use of Extended Reality technologies to address perceptual complexity by visualizing operational scenarios and proposes designing for changeability as a mechanism for creating value-robust circular systems.