Your POV sounds too paranoid to be credible. You seem to ignore the fact that it's the way the ideas are expressed that is copyright not the ideas themselves.
Of course, I don't want to deny the fact that people can claim another interpretation of the copyright law and try to argue that additions are derivative works. But that's just as like going to the police and trying to convince them that the house of my neighbour is my house.
It's quite clear that as an initially copyvio passage is more frequently edited its resemblance to that text changes, and the degree of copyright violation diminishes.
That's not the trick.
Additions are original works and the good way to do is to go back to the sane situation, to erase the copyvio text and to re-add everything that is not directly based on it.