I have no idea how easy or hard implementing that would be from a programming standpoint, but you would still need to go through the file after such a mass change to fix all of the cleanup issues that will likely result from moving the justification lines without moving the walls. That said, there are times when I wish I could change the justification of many walls at once without moving them, too. (Even when done manually, you need to make adjustments to cleanups.)
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David Koch
Autodesk Discussion Group Facilitator
Using ADT 2004 at work; access to 2005, 2006, 2007 & 2008 at home