Systems of systems (SoSs) constitute a particular class of systems, whose constituents are themselves systems in their own right. Such systems present architectures that dynamically change in a way that is not necessarily intended at the time of design. We target a kind of SoS that is subject to evolutionary development and propose a reconfiguration design process that guides the architect in charge of SoS engineering by indicating the tasks that must be accomplished to develop a reconfiguration for evolutionary development. Finally, our process is applied to design a reconfiguration in the context of a realistic case study inspired by the French emergency services.