alt Hacker NewsI actually posted ntsc-rs as it came up in my research - I'm also looking for something like what you're describing..!
I was also looking into https://codeberg.org/fsphil/hacktv which generates a variety of different analog tv signals (meant to be broadcast using HackRF) - but yes, I want the opposite - an analog-receiver-emulator...? And one that would be "ok" with incorrect signals // fail like an analog TV would... :-)
Slow scan and fast scan television encoders and decoders exist, probably the algorithm is public domain, so you can just increase the bandwidth and speed until you get what you're looking for, then you can tamper with IQ .wav files to edit the "signal".
It can't be that hard for someone with skill and determination!