In response to the challenges related to integrate human considerations within complex interactive systems, the Human-System Integration (HSI) initiative has been proposed. Nevertheless, the HSI approach is difficult to fit efficiently into the system engineering processes because of the lack of shared methodologies, modeling semantics and tools. This paper focuses on the needs for a new methodology and an adapted formalism to improve the collaboration between the system engineers and HSI practitioners. It concludes with the presentation of our methodology based on the Model-Based System Engineering (MBSE) and the SysML modelling language.