Roland
Moderator
Never have I ever scrapped an item to craft a worse version of the same thing. I don't think. Could I do it? Yeah, I know I could, I've crafted "roughly equal" main things my whole A21-SP experience, and none of the things I've done in game have required excessive cheese yet.
The reason for doing such a thing would be to test out the idea that the trader only gives parts. If you wanted to actually playtest that idea then you would scrap any weapons received from the trader to simulate getting parts instead and then craft the best you could.
So technically it is silly to scrap a better weapon for a worse weapon if you are playing the game the way it is presented but if you are pretending that traders don't give weapons to test out an idea then it makes perfect sense.