Rapid responsiveness to diverse customer needs is considered a competitive advantage in manufacturing business. To shrink the inquiry-to-order process, manufacturing firms will benefit a lot from building a product configuration system (PCS) which is the enabler of mass customisation (MC). PCS has matured in consumer businesses for decades but in capital goods industries, typically operating in engineer-to-order (ETO) manner, things differ a lot. It is for the reason that conventional PCS is incapable of extending customisation from order-delivery processes to the design/engineering phase. Cloud manufacturing, which is an emerging service-oriented manufacturing paradigms enabled by cyber-physical system, the Internet of Things and the Internet of Service, is promising to break the bottleneck of "ETO PCS" by the provision of technical infrastructure for product, service and data customisation. With the introducing of manufacturing-as-a-service (MaaS) concept, a product family is extended to a product-service family (PSF) in this paper for implementing in-depth product configuration process with scalable customisation depth (i.e., the degree of customisation freedom). Additionally, an approach of service delegation in product configuration process is proposed to support customer-centric product customisation. At last, the methodology proposed in this paper is validated by a case study in which the product configuration process of a complex ETO product is performed.