Requested feature overview description.
The current system for replacing a post with a larger version of that post is as follows: Upload the larger version as a new post. Set the smaller version to be the child of the larger version. And request to delete the smaller version with the reason that it is inferior to the larger version. Then you wait for someone to come by, see that it's all good, and approve the new picture while deleting the old one. Oh, and don't forget to copy and paste the tags from the small version to the big one.
Not only is this needlessly complicated to newcomers who might want to help but have no idea where to start, but this also wipes everything else attached to that post, such as comments, tags if you forget to bring them over, upvotes and downvotes, favorites, original upload date, notes, etc.
Rather than this nonsensical process, it'd be great if there was a button that said "Upload larger/better version". You'd go to it, it'd ask you to upload the picture, and then you wait for someone to come by, see that it's all good, and allow it to go through. The post gets updated with the superior version, everything else is maintained. Except for the positioning of the notes, that would be screwed up a little, but it's an easy enough manual fix.
Why would it be useful?
The main use this would have would be to preserve comment sections. There are some quality gems in those, and a larger version overtaking it can lead to those gems being inaccessible. There's also the preservation of notes, which is important because there's a lot of translation work in those, and it's time-consuming to recreate them in the larger post at the moment. This would also guarantee that the tags make it over to the new post, as well as the description, views, rating, votes, etc. And finally, it limits the number of new deleted posts coming in, which is good for the system as a whole.
What part(s) of the site page(s) are affected?
It affects very little on the site pages. There's one new page, the Upload Superior Version page, and there's a new button on posts that leads to it, but otherwise, it's roughly the same. There could always be changes to the upload date/user stat, with two dates, corresponding to the original upload date/user, and the update upload date/user, but it's not that important.