Dynamic and heterogeneous service-oriented systems present challenges when developing composite applications that exhibit specified quality properties. Resource heterogeneity, mobility, and a large number of spatially distributed service providers complicate the process of composing complex applications with specified QoS requirements. This PhD project aims at enabling the efficient run-time generation of service compositions that share functionality, but differ in their trade-offs between multiple competing and conflicting quality objectives such as application response time, availability and consumption of resources. In this paper we present a research roadmap towards an approach for flexible service composition in dynamic and heterogeneous environments.