I do not think we need to add this to page settings. I do not see other sites on the web that have different copyright info on different pages so I don't see this as a common scenario. One can always add a copyright notice right in the content of the html or blog if they need to. Also content may exist on more than one page, if there was going to be a setting for copyright it should be on the content instance not the page because content instances may be moved and the page has no way of knowing about the copyright of the content on its contained instances of content, (nor should it have any knowledge of it as a matter of separation of concerns design principal)
Maybe someday I'll add it as a property to feature instances but its a very low priority. I already have an ambitious list of things to do on my roadmap.
You are free to make suggestions but it is unlikely that I will diverge from my own plans.