What are the dependencies, other source files from the project or external dependencies that need to be resolved from some external source?
EDIT: I guess I was kind of bored tonight 
I made a small sample that can read extra input source files from an initial source file https://github.com/oesolutions/gradle-embeddedinputs-test The key to this is not overriding getInputs but instead providing the annotated methods, which Gradle will call.