Allow creating mirror type index

Hi, Are there any plans to allow creating mirror type indexes in addition to stage types? That way if I have say a company pypi server somewhere with packages I could add an index in my local devpi to be a mirror of it, and then it could be base of other stage type indexes I create. This question seems to imply this is almost possible: https://groups.google.com/forum/#!searchin/devpi-dev/mirror/devpi-dev/tJp2Xi... But just needs to allow the upstream index-url to set for the mirror (and not crash of course). Thanks, \Peter