The rapid evolution of customer demands has posed new challenges to manufacturing, leading to a shift towards mass customization and customer-centric approaches. This paradigm shift, driven by advancements in technologies such as additive manufacturing and digital technologies, has transformed assembly systems into smarter and more autonomous entities. However, the design and planning of assembly systems in this new context require greater speed and resilience. This paper proposes a digital twin-enhanced smart assembly system design for resilient operations to confront this challenge. The proposed design process leverages digital twin features and identifies several possible services enabled by digital twin. The paper also presents a framework for the digital twin-enhanced smart assembly system and discusses its implications and future directions.