Mouser,
Have you though of facilitating end user use of the .dcupdate file by reserving a part of the namespace for the user to allocate knowing nothing that you do will trample over it or be ruined by uncoordinated content.
For example, a sub item called "user" in which all user entities are mapped would achieve that end. dcUpdate would just ignore that part of the xml tree, and the user could use it as he wishes.
Perhaps it would be wise to declare a rule on the maximum size of the .dcupdate file, perhaps 10k would exceed reasonable needs.
Cheers
Owen