I don't think you want your backups in Google Docs either, given that Google may decide to ban you for TOS violations at any time.

I really do think videos would would work, reliably, given sufficient redundancy. Again, we have QR codes already, so this is a proven idea. You can't make QR codes unreadable without removing lots of perceptual visual details. The risk, as with using Google docs, isn't that Google will change their encoding, but that Google will just take down the videos for service misuse.

I think it would be comparatively more difficult for Google to detect this stuff in a video compared to a text document, because you expect some videos to be long and large. The entirety of the Encyclopedia Britannica comes out to less than 500 MB in a .txt document, so using any reasonable amount of space in a Google Doc should quickly raise red flags.