Arbitrary upstream repositories: on the roadmap?

Hello,

I am interested in using CodeArtifact in some projects. We currently use several Maven repositories which, while public, are not on CodeArtifact's list of supported upstreams. Unless I am mis-reading the documentation, it's not possible to use an arbitrary upstream repository outside the approved list (which, for Maven, looks limited to Maven Central). Is this a feature that's on the roadmap for CodeArtifact?