Cloud computing is well suited for applications with a distributed architecture and dynamic demand of resources. Yet, current approaches to model cloud application deployment do not cater for the application's dynamic nature and its rapidly changing business requirements. The static description of deployments results in a lack of reusability and also lacks an integrated way to adapt to the current context. To reuse and refine the deployment model, we introduce a simple decision layer on top of a cloud application description, which abstracts from the actual deployment language and allows assembling the deployment model from existing model fragments. Those fragments are chosen based on the input of the decision process. We define an architecture for the decision layer and sketch an implementation based on CAMEL, DMN, and ADOxx. The benefits of the decision layer are illustrated by two use cases. Our approach shifts the focus from a static to a dynamic and reusable modelling process, which also reduces the modeller's effort.