In recent decades, the aims and objectives of education -- and therefore public discourse on the appropriate skills and attributes of mathematics teachers -- have been rapidly shifting due to forces from outside the teaching profession. The forces driving change in mathematics are as diverse as the emergence of "Industry 4.0" and "STEM," new directions in transnational education policy making, and the COVID-19 pandemic. This paper contributes to a growing literature seeking to empower teachers to respond to the complexity of such multifaceted change expansively rather than defensively. It does so through the refinement and application of practical theories of educational change and approaches to building actionable practice knowledge. Specifically, this paper will argue for the use of the "epistemic object" as a practical focus for changes to practice chosen by the profession. This argument will be made within the framework of "practice architectures" offered by Kemmis and others. The paper first considers the impact of some recent disruptions on teaching and then provides a "worked example" of using mathematical proficiencies as an epistemic object able to practically support teachers to develop actionable knowledge grounded in the specifics of their own professional context.