Stargate SG-1 is already completely in HD, just not released for whatever reason on blu ray. Wouldn’t be worth it to work on that show.
Perhaps, but I had the “pleasure” to watch some of that HD-Versions, while seasons 8-10 are in what I would call “decent HD”, seasons 1-7 have been done by SyFy, and they are really soft and show signs of aliasing, therefore I think perhaps going from the DVDs would be better.
Anyway, I am not going to work on it today or tomorrow, perhaps something will change until I get around to it.
As you said, seasons 1-7 are just upscaled from SD sources for Syfy, and not well at that. Seasons 1-3 were filmed in 16mm and 4-7 in 35mm, the difference between the two sticks out even more with that release. The entire run needs a TNG-R-style remaster to be properly in HD.