When building a POM project with a site descriptor, this change causes a linkage error on XmlSerializer (from Xpp3Dom). Looking around on the java forums, I found this:
which seems to hint that processing the Xpp3Dom class to change package names for anything at all might cause this problem. I'm not entirely sure I understand this problem, but I'm adding a new IT to the core-integration-tests to check this scenario for future changes.
Unfortunately, this issue won't make it into 2.0.10 as a result. This problem seems to indicate a level of risk for this change that I'm simply uncomfortable with at this stage.