I THINK I might have found an answer, but I'm too chicken to try it in the real, live job before I get confirmation from our Sawtooth mates that I'm not doing anything stupid.
I saved my job as a test job, and created a test database. I then opened up my saved data (the stuff I want to import) and played with the file a bit. Had to delete the columns at the end holding constructed list results and the like, delete the column row, etc. I also added 30,000 to each of the respnums just in case. (There's between 16,000 and 17,000 in the sample so figure that will be safe). Then I imported my data through cpanel. And ... oh wonders ... the admin module updated!! I tried a disqualified case ... all good. I tried a partial complete - all beautiful.
Gotta be a catch ... can anyone see any reason why it wouldn't work?