"No because part of what copyright is about is protecting the content as well, copyright holders get to decide what modification are made prior to distribution, if they are no longer allowed to do that then they've lost half of why copyright exists, and with that half gone it won't be long before they start losing the money (hey why should you pay somebody for a product that you modified before distributing, it's just as much your product as theirs at that point)."
Your argument falls flat on its face. As long as the creator is paid in full, there is no problem. As long as GM gets paid for its car, I can modify it any way I want.
Cars are not copyright protected.
Modification of copyrighted material already gets used to not pay people for it. Just earlier this year some CD (I forget which one, some band I don't like) was re-issued for an anniversary edition, inbetween when the album first came out and this anniversary edition the original drummer had left the band and angered the other members so for the re-issue they deleted his drum tracks and had someone else redo them all, end result is he doesn't get any royalties for the re-issue CD because he doesn't appear on it. Once you allow anybody to modify copyrighted material before the sale then the question of who gets paid becomes wide open.