With the change of EU regulations in the automotive market in 2002, multi-brand car dealers became possible. Despite the high economical expectations connected with them, the existing IT infrastructure does not provide satisfying support for these changes as it had been developed independently by each brand for many years. In this paper, we describe a solution which supports rapid prototyping by combining a model-driven framework for cross-organisational service-oriented architectures (SOA) with an agent-based approach for flexible process execution. We discuss advantages of agent-based SOAs and summarize the lessons learned.