Global computing platforms have become popular tools for the resolution of large scale problems. They are often independent without any interoperability between each other. Therefore, clients are now asking for a better availability and scalability. In previous work, we presented the YML framework which was a first attempt to enable the development and deployment of applications on several global computing middleware. However, it suffered from scalability issues and a static approach. In this paper, we highlight recent extensions of YML. We achieve a dynamic federation of computing middleware because YML is now able to manage at the run-time several middleware back-ends. Other improvements such as an OmniRPC back-end, a component binary cache mechanism, a new data management module, and a new data type supported by the YML front-end, yield to a much better scalability. We present the first evaluations of these extensions on a network of workstations and with a typical distributed sort application. Although the results show a significant overhead, they stress the benefits of binary caching and dynamic back-ends federation.