1. A design optimization system, comprising: (a) an initial design evaluation module evaluating a system model using initial subsystem designs to extract interactions at least one of: (i) between subsystem models; or (ii) between the system and the subsystem models; (b) an updating module updating the interactions for the subsystem models; and (c) an optimization module performing subsystem design optimization using the subsystem model and most recently updated interactions, thereby obtaining an updated subsystem design.