Figured you'd want to know, but those signatures are probably just from the creators themselves, not like a special variant or anything. Most 90s Image books had people signing them left and right at conventions back then, so they're not exactly rare. You might get a little extra from the right buyer, but honestly, they're mostly just fun shelf filler for anyone who loves that era.

Twenty years of butterflying corners and one old guy changes your whole world, that's a wild thing to hang your hat on. I mean, did the building fall down before? Was every corner you ever did some kind of crime scene? Straight joints look fine, sure, but so do wings when you get the mud right. Sounds like you're just tired of the extra pass, not that you found some secret truth. Give it a month, you'll probably go back to what works when a door frame is slightly out of square.