Maintenance and inspection systems for future fusion power plants (e.g., STEP and DEMO) are expected to require the integration of hundreds of systems from multiple suppliers, with lifetime expectancies of several decades, where requirements evolve over time and obsolescence management is required. There are significant challenges associated with the integration, deployment, and maintenance of very large-scale robotic systems incorporating devices from multiple suppliers, where each may utilise bespoke, non-standardised control systems and interfaces. Additionally, the unstructured, experimental, or unknown operational conditions frequently result in new or changing system requirements, meaning extension and adaptation are necessary. Whilst existing control frameworks (e.g., ROS, OPC-UA) allow for the robust integration of complex robotic systems, they are not compatible with highly efficient maintenance and extension in the face of changing requirements and obsolescence issues over decades-long periods. We present the CorteX software framework as well as results showing its effectiveness in addressing the above issues, whilst being demonstrated through hardware that is representative of real-world fusion applications.