Extrusion-based 3D concrete printing (3DCP) enables geometries that are difficult to realize using conventional formwork, but their translation into load-bearing building systems requires coordinated consideration of structural design, material behavior, printing, reinforcement, building services, transport and assembly. PRINTCON—3D-Printed Modular Architectural Structures—investigates prefabricated printed components belonging to controlled families and connected into larger structural assemblies. Topology optimization is used as a structural form-generation method; within a defined architectural design domain and for prescribed supports and loading conditions, it identifies principal force-transfer paths and an initial material distribution. The resulting form is subsequently regularized to ensure printability and enable reinforcement integration, then divided into transportable segments and detailed for jointed, post-tensioned assembly. This conceptual paper develops a constraint-oriented workflow; organizes the relevant inputs, design variables, constraints and verification requirements; and formulates a focused research agenda for subsequent numerical and experimental work.