I have built a prototype to generate a list of maven dependencies based on the XML QName of the implementation/binding/policy types. See:
This tool will provide the ability to parse the deployable composite to find out what extensions are required to support the given SCA application. It will then produce a Tuscany-enabled web application to package the required Tuscany and 3rd party jars. It would be nicer if tool can automate the deployment of such web apps into Google App Engine.