Hi randomexpert,
I've read your document, and found that it is rather similar with one of the Drupal module i used before, called 'feed' module. I used to use that module to import CSV file from local, to create new nodes.
Since you mentioned that the import process is already built, and meant not to be modified, I believe I can achieve what you desired in you phase 9.
What in my mind is that first i'll need to modify the fields of content type to the desired 6 field, and then i'll work on the batch import code to find out the matching part that match data from file to the node's field, and from there i'll modified the code so that it match correctly.
I'll need to see those codes in details to get a better idea. I proposed that i can fixed it in 1 night time (after back from work ) , I'm from Malaysia, same time zone, so if you are interested let me know tomorrow so i can be prepared :)
Look forward to work for you.
If I can't deliver, you don't have to pay me. I just hope to get my first project in freelancer, and got a good review.
thank you
regards
JY