I've released a final standalone version of xml2po as 1.0.8. It has some simple changes in the code to support preprocessing document trees and outputting special messages for translation (this is used for handling stuff like images in DocBook documents).
On the more important issues, I finally (lazy, lazy me—Shaun, sorry about being so slow) imported it into gnome-doc-utils module. I went with the easier solution: I imported everything, and I'll remove/clean up a thing at a time.
This ensures that it's already buildable and installable on most systems (or at least as good as xml2po 1.0.8 is). It also means that it is not yet built by default with gnome-doc-utils module, but that will be resolved when it gets completely integrated into gnome-doc-utils.
So, lots of work left to do, but at least we're getting somewhere.