Flexibility is a major concern in engineering design. This paper examines two complementary approaches to designing flexibility into engineering systems. One approach, based on system decomposition, emphasizes a one-to-one mapping between form and function, as in modular designs. The second approach decouples form from function, enabling a many-to-many mapping, as in layered designs. These approaches need not be mutually exclusive; rather, they can be synergistic. These claims are examined using simulated intermodal shipping networks. Implications for system design are discussed