Choosing one or more conceptual modelling languages as part of a Model Based System Engineering (MBSE) approach necessarily involves “professional introspection” in order to clearly define the motivations (modelling intentions) to be supported. No matter which choices are made, they are less important than the justifications that lead you to make them, and the know-hows that they are used to magnify. Communications, which are fundamental to the success of an MBSE deployment project, must be based on these know-hows. Finally, the deployment of MBSE is a long-term, incremental process that takes place at differing paces within an organisation. The command of the coherency of the models and the corresponding intentions must be considered as a major issue.