At first I thought you had a point (and for practical purposes, perhaps you do) but I don't think it'd be particularly challenging to inject video frames into a stream without re-encoding the original video.

It’s not challenging.[a] ffmpeg can “join” streams back-to-back without reencoding if one desires.

[a]: This is assuming you know the magic incantation to get ffmpeg to do it

You just need to make sure the video sections are stored in a concatenatable format (like mpeg or m4s), and then you can literally use cat.

if anyone has the resources to figure out this magic incantation, it would be Google.

It’s not that difficult a command compared to what is possible with ffmpeg. But it’s also a pretty common enough task that literally the first result for using DDG with “ffmpeg concatenate without reencoding” gave: https://stackoverflow.com/questions/49371422/how-to-merge-tw...

You can cut on any key frame and switch to another video.