There are systems in the field of event-driven control that require continuous operation. Continuous operation is achieved by switching from normal control to control capable of coping with faults when a fault in the system is detected. In the design phase, the developer needs to create an update controller capable of coping with all possible faults by modeling safe update procedures for any number of possible malfunction patterns. This naturally places a heavy burden on the developer. In this paper, we propose a design method that reduces the design cost of the update environment, which accounts for most of the design burden of an update controller. When designing a new update environment by reusing one that has already been designed, only the design related to the state preservation during update needs to be changed. However, the conventional design method utilizes not only the state preservation relationship but also mixes in two other concerns. Therefore, our proposed method separates the preservation relations of this state from the mixed concerns. We examined the reduction effect of our method in a reuse situation with multiple failure patterns in two systems that require continuous operation and found that the maximum design cost reduction effect was 90% or more.