I had a run-in with a chrome plated plastic dustcap that nearly got the best of me, so I can imagine how much of a nightmare a seized aluminum one would be. I eventually picked all the bits out and saved the extractor threads.

Having said that, since the DS arm came off, I would have cracked the lockring and removed the NDS cup, then tossed the lot into a bucket of Kroil to soak for the duration of the tour