[cybmole]

you are right in that there's a history of similar requests on amazon forums and no solution.
but I'd still try a call to amazon CS , say you have a new PC and ask them to push all 17,000 books to it for you.

failing that, an ad on craigslist for someone to sit & do 17K double clicks for you ???

It's probably not that bad, actually, I assume that many of the 17k are freebies, so as you "can't remember what 10% are about" even, just forget they ever existed. If ever you mistakenly try to buy one that you already own, amazon should pop up " you purchased that on.... " so you'll know to check your cloud.
why clog calibre with thousands of books you have no desire to re-read ?

Final idea, you may be able to get a printed list, at list, via goodreads. when you link goodreads to your amazon account , I think goodreads can/ will pull in all the amazon titles you ever bought, and invite you to rate them.
You don't actually want to rate them, but once goodreads has the list, maybe it can do something helpful with it , like sort it in various ways at least ?