This paper presents a systematic design approach to the development of functionally integrated mechanical-electrical lightweight systems. The development of these systems requires the end-to-end consideration of all product domains involved, aspects of lightweight design and their mutual interdependencies. To manage this complexity, a specialized approach is developed, which extends the V-model of VDI 2206 problem-specific and purpose-oriented. In line with the proposed approach, this work presents the conception and evaluation of three functionally integrated on-board receiver units of automotive wireless power transfer systems for electric vehicles. These concepts provide a significant reduction of the vertical dimensions, which significantly increases the applicability and transferability of wireless power transfer systems.