The best way to perform any automation when it comes to auto-blogging is to import ALL data to a stand-alone database table. One created per .xml or .csv file.
Then from there we work with the data. Using that database table to track what data has been used. Updating the data and then applying it to posts when ready.
May sound like opinion. But all approaches have been tried and tested in Easy CSV Importer over the last couple of years and the benefits of getting the data into the database as a first step are great. Better control and avoidance of running into issues once the auto-blogging begins.
