I got all the 1komas backed up, I will sort through them and organize them for archival later.
I also figured out what is getting taken down at the same time as the DMM version of SS tomorrow. In the same section as the 1komas, gekijou wide, and cinderella post there's a section called Cinderella Theater that has all the old U149 extras, Cingeki, Gekstage, and other random videos.

There's one small problem though, even though none of it is supposed to go down for another 18 hours, I can't get any of the videos to play in the DMM or Android version of SS. The U149 stuff was backed up by an anon here and should be in the archive, if someone wants to confirm that the links are still live. Cingeki and Gekstage are backed up in multiple places. I have no idea about the stuff in the others tab. Unless someone knows a filename to give to an asset downloader, I don't know how to get them.

3D commus and Radio Calisthenics are also being removed, I think, but I have no idea where they are in-game. If someone can point me in the right direction I can check it out. Or better, rip/record them themselves. I was going to start on backing this stuff up a few days ago but an emergency came up and I was unable to really do any computer work for a few days. I only really have like one more hour after work before the game goes down to mess with it.

Reminder of what's getting removed on 8/21:
>>529620549