Combat system effectiveness simulation (CESS) is a special type of complex system simulation. Three non-functional requirements (NFRs), i.e. Model composability, domain-specific modeling, and model evolvability are gaining higher priority from CESS users when evaluating different modeling methodologies for CESS. Traditional CESS modeling methodologies are either domain-neutral (lack of domain characteristics consideration and limited support for model composability) or domain-oriented (lack of openness and evolvability) and fall short of the three NFRs. Inspired by the concept of architecture in systems engineering and software engineering fields, we extend it into a concept of model architecture for complex simulation systems, and propose a model-architecture oriented modeling methodology in which model architecture plays a central role in achieving the three NFRs. Various model-driven engineering (MDE) approaches and technologies, including SMP, UML, DSM, and so forth, are applied where possible in representing the CESS model architecture and its components' behaviors from physical and cognitive domain aspects.