The design of embedded mechatronic systems like electromechanical actuation systems involves heterogeneous knowledge due to the interference of several engineering specializations and the multiple physical laws that govern their behaviour. This results in costly iterations during the design process and non-optimal solutions. Multidisciplinary System Design Optimization techniques provide theoretical foundations and computational tools for optimizing large and multidisciplinary systems. The approach taken uses these techniques within a proposed design and sizing methodology. It allows a holistic sizing of mechatronic engineering systems with emphasis placed on reusability and rapid decision making. This methodology has been applied in an industrial context to size an electrical thrust re-verser actuation system. This more integrated design approach has resulted in significant assessments and insights in early trade-off studies for this complex aircraft subsystem.