A few updates:
Fellow Pyrate AstralStorm gave me a good idea while I was streaming last night, and I realized that I do not have to destroy the remaining working K1000 driver to do this transplant. I can simply create a 3D model of the spider/earcup assembly that fits an HD800 driver instead of the stock driver as a replacement. So, my plan of action has changed thusly:
1: I will continue trying to get in contact with AKG. If they are able to fix the broken driver, I will have them repair it and send it back to me.
2: While it is not fair to pass judgement with only one working channel, being driven out of an Objective 2, I was not impressed by the sound of the stock K1000. I have a small speaker amp coming in the mail and I will see if my impressions of it change with that.
3: Regardless of the outcome, I will 3D print the new spiders and order a pair of HD800 drivers from Senn. I'll choose which one I like best, and either sell or keep the remaining drivers.
I'm making some changes to the OP now. Stay tuned.