Allow blob:// videos to be saved normally. It’s just a file. I’m looking at it. Move it from memory to the hard drive.

True. Although in many cases this is indicative of a stream (not really a traditional file for the browser), but at the very least, even in the (rare?) cases that there isn't cached content already, it should theoretically be possible to start saving the video the moment you press on the save button...

Already the "picture-in-picture" mode Firefox offers is a step in the right direction, imho. It allows the browser to take over control of the playback, which is something some places try to forbid.