Like I said, Flash itself will not stop existing. Like Windows 7: a lot of tech website called, in early January 2020, "Windows 7's death". It still exists today and functional. I use it right now. It's just not supported and the same will be for Flash. You will always be able to use forks of Chromium and Firefox to load the plugin and see flash objects on an old website / sites that embed them. Or use older versions of Firefox or use Internet Explorer (LOL) to use Flash. Will it be recommanded? Of course, not. The option will still be there. However, of course, moving them to archival project that doesn't need to find a way to install Flash is the best case scenario.
I'm using "dead" as shorthand for "regular people shouldn't run this". Obviously you can keep "dead" software alive, but there's usually a good reason software should be "dead".
Sure, you can keep Flash alive with an old (insecure) web browser browsing old (possibly insecure) websites and running an old (insecure) web plugin. After 2020, no regular person should run this setup.
As for "archival project that doesn't need to find a way to install Flash is the best case scenario" Flashpoint is exactly that project lol. It includes an isolated Flash Player that doesn't need to be installed.
Ideally Flash would be fully emulated (e.g.
Ruffle) so we don't need flash player at all, but we're a long way off from that.
personally i don't see any difference between downloading flashpoint and just downloading adobe flash player and saving the SWF files you want off of the websites they are hosted on. if anything the latter is probably more space-efficient. i however do agree that a comprehensive list of touhou flash content should exist, so people who are looking for some don't have to search through itch, dagobah and other sites
For most SWFs (and frankly most Touhou SWFs) you're right. But some flash games have "sitelocks", aka they refuse to run unless they're hosted on the website they were downloaded from. Other games depend on external files and resources from hardcoded locations. Flashpoint implements mechanisms to work around all of these issues, to meet the goal of preserving as many flash games & animations as possible.
To stay on topic: I found the original SWF for Cirno's Perfect Math Class on archive.org:
https://web.archive.org/web/20090204020717if_/http://www.iosysos.com/mp3/IOSYS_toho9_SansuuKyoustrawberriessu.swf
Thinking of packaging it up myself for Flashpoint, though if someone else does it first that's ok too.Edit: I submitted Cirno's Perfect Math Class, as well as Marisa Stole the Precious Thing. If all goes well, both should appear in the next Flashpoint release.