An error occurred while saving the commentoneil commented
This would be a great feature for migration teams to allow site users to test their sites/workflows/lists etc. When users test they may want to create/modify items in the destination to ensure they feel comfortable that everything is working. If the do create/alter items at the destination, then they need to clean things up/undo changes and most of the end-users we work with tend not to be able to do this well. If they don't clean things up, then the incremental would skip items that are more recent in the destination.
If this feature existed, migration teams could avoid having to identify sites that were tested in this way and do full migrations (after testing).