Allow the workflow to (visually) configure an SCM, check it out into a workspace on the Jenkins master, and load a sandboxed Groovy script from a defined location in that workspace.

Perhaps allow the workspace to be treated as a sourcepath so libraries can be imported.

Optionally include the flow SCM in polling and/or changelog generation.

Abandoned ideas:

1. Construct URL with an instance of URLStreamHandler we can create a URL space that can access files over FilePath, and somehow prevent the class loader from continuing to use the workspace after it goes out of scope.
2. Similar but the URLStreamHandler uses SCMSource to access files without ever checking out anything.