Probably not. I was thinking of vampire tapping the video signal on the logic board connector, and that's just a B&W signal, which I'm 99% sure is generated in hardware where no amount of ROM code changes will make a difference. But if you tapped into the CPU bus, and snooped writes to the video memory, you theoretically could build something that generates a video signal in whatever format you want. Or just transmit the video memory contents to a PC for remote display. That's the approach bbraun has taken with his video project for the Mac SE.