So, suppose there is an app in the store. I generally need this app, but it misses a feature, I need. Or I am not too happy with the overall user experience and improve parts of it so it better fits my needs. I add a feature, even if a small one, I adjust the user interface the way I like it. For me this app is definitely better than the original, perhaps for others, too. Does this count as copying? Who has to decide this? How different has an app to be to count as work of its own. Or are we all cursed with inferior apps, because they were developed more quickly, sloppy and therefore released earlier?
Proposals like yours are quickly made, but rarely thought through. They would work fine, if there were only black and white cases, but there never are. As experience in many areas shows, only wannabe block wardens and lawyers benefit from rules like that.