Just so I understand what you're advocating - you're advocating that, if I, an artist, drew a picture of Mario from Super Mario Brothers, I should be able to sell that picture on some sort of physical media (button, pin, etc)?
Why not? It's your work. You can't really be competing with Nintendo, because they can't create that same picture, because they don't employ you. Also you are extremely unlikely to be making a material impact on the bottom line of a multi-billion-dollar international media company.
Also, this is a thing many people already do, so I'm really advocating that it's fine for them to continue doing it.
I don't think the fact they are a multi-billion dollar company has any bearing. If it does - where do you draw the line? Is it always okay regardless of the income of the original creator?
It gets stickier when you dive into other types of derivative work. Let's say you write a book and I translate it to Spanish. It's my translation of your story. Based on your framework, is it okay to sell at conferences in paperback form? If not, how is it any different than drawing a character I created and selling it on buttons?