Mechanical product engineering is a research and industrial activity which studies the design of complex mechanical systems. The process, which involves the collaboration of various experts using domain-specific software, raises syntactic and semantic interoperability issues which are not addressed by existing software solutions or their underlying concepts. This article proposes a flexible model-based software architecture that allows for a federation of experts to define and collaborate in innovative design processes. The presented generic approach is backed and validated by its implementation on an academic usecase.