The German air rescue and healthcare system is facing a number of changes and challenges, that require a rethink in the development of new rescue helicopter concepts. As part of its research activities, the German Aerospace Centre is, therefore, developing the concept of a medical deployment vehicle as part of a future and alternative rescue helicopter fleet. New economic, technical or performance-related framework conditions go hand in hand with necessary changes for the cabin interior and a large number of different user groups. In order to capture the large and diverse requirements spectrum and to translate them into future cabin interior concepts, a deep understanding and involvement of key user groups in the early design process is necessary. Human-centered design methods such as Co-Design offer a wide range of possibilities here. As part of Human-centered Design, the Co-Design approach is an important method, enabling the collaborative development of complex concept ideas among designers, end-users and various stakeholders. Through early and active involvement, Co-Design facilitates the incorporation of users' emotional factors and experiences with a product, enabling an iterative feedback and optimization process. This allows designers to gain an enhanced and quantifiable understanding of different user experiences and to create concepts from the perspective of the user and their context. Additionally, and merged with Co-Design, immersive technologies such as Extended Reality (XR) offer high potential to make future concepts feasible and to implement requirements and optimizations in real-time. In light of the diverse possibilities offered by combining the Co-Design approach and Extended Reality, this paper presents the applied XR Co-Design approach for the design of a future medical deployment vehicle cabin design concept. The methodological approach therefore follows two steps. First, to gain deeper insight into the experiences and requirements of different user groups in their professional context, an online survey was conducted. Using an informative online booklet, user groups were provided with an initial glimpse of the new concept and enabled to establish a connection between the novel concept and their own requirements. In the second part, an immersive Co-Design workshop allowed user groups to develop their own creative ideas and translate them using virtual reality and a digital prototype. The presented XR Co-Design approach demonstrates an effective method for developing complex cabin interior concepts and offers versatile application points for transferring the method to other transportation concepts of the future. At the same time, the workshop results provide a precise and human-centered basis for the detailed design of a digital medical deployment vehicle concept for the future.