PIO is indeed awesome! A while ago I was wondering if the RP2040 could be used as a scandoubler (and talking about it with the Chrissy who left a comment on your blog). I was originally discouraged and decided to not pursue it because the ADCs on the RP2040 are just too slow to capture video, so I'm happy to see the results of your effort!
You can capture video in a weird format with PIO on one core, and output it with PIO (in a standard format like VGA, or even DVI) on the other core, like here: https://blog.qiqitori.com/2022/09/raspberry-pi-pico-15-6-khz...
Or you can implement old DACs that expect a weird input data format, to a certain extent, like here: https://blog.qiqitori.com/2023/03/raspberry-pi-pico-implemen...
(Now I'm almost at the end of my sabbatical but think these projects (and others) were totally worth doing even if it meant living off savings, heh.)