Most formal models are used in detailed design and focus on a single domain. Few effective approaches exist that can effectively tie these lower level models to a high level system model during design space exploration. This complicates the validation of high level system requirements during detailed design. In this paper, we define requirements for a high level model that is firstly driven by key systems engineering challenges present in industry and secondly connects to several formal and domain specific models used in model-based design. We analysed part of the systems engineering process at a company developing complex systems, by observing the design process and by analysing design documentation and development databases. By generalizing these observations, we identified several high level systems engineering challenges. They are compared to literature, focusing on reported systems engineering challenges and on existing approaches that incorporate high level models in model-based systems engineering. Finally, we argue that high level system models supporting design space exploration should be able to communicate information regarding design trade-offs (e.g. safety versus ease of use) effectively in a multidisciplinary setting. In our outlook, we propose how to continue our research, by recommending further research and defining a research question.