This research proposes a systemic framework for the understanding of client requirements in Information System development that is particularly relevant for project contexts characterized by diversity of stakeholder values and significant complexity. In spite of the strong research tradition associated with Soft Systems Methodology and the growing interest in the Work System Method, the level of use of those by practitioners is not high as such situations require harnessing the strengths of more than one methodology. The paper explores the selection of techniques from three systems methodologies and mixing them to be applied in the process of requirements understanding by clients. The mixing of methods from various methodologies is justified through the principles of Critical Systems Practice and the process of their use is guided by Action Design Research. The contribution of the paper for the field of Information Systems is in the proposal of a more powerful framework for promoting organizational learning about software requirements understanding by clients.