I just want to know one thing. If I decide to make a walking dead topper, identical or even of a lesser quality, and maybe sold cheaper than stern. Does that make it ok for the industry? Would Gary be happy? Would Stern be happy for someone's good fortune in getting a better price or product they currently do not manufacture. Maybe I can make Metallica LE's any buyers

Good question.
It gets down to copyright.
Ask someone like Pinnies4me who knows all about this stuff.
If there is a market for something, go for it, but stay within the law obviously on any Mod parts.
Maybe working with the manufacturer would be a good idea. Mods under licence is a win win.
Speak to Stern if u are serious. Swinksy makes a lot of great mods and has researched what to do to stay within the law etc.