ITT: lots of the usual paranoid overkill. If you do rsync with the --backup switch to a remote box or a VPS, that will cover all bases in the real world. The probability of losing anything is close to 0.
The more serious risk is discovering that something broke 3 weeks ago and the backups were not happening. So you need to make sure you are getting some kind of notification when the script completes successfully.
Fairly simple using Python locally with no need for a server: requests-html to get the website front page, then loop through the articles using feedgenerator to increment a feed object, then pipe it as XML to a file.
Obviously this is not simple at all but it does work. I have been consuming an RSS-free site by RSS every day for the last year. Provided you ensure theguid for each item is its URL, the RSS reader will keep track of what you have seen already, in order, which of course is the magic feature of RSS.
But
rsynccan do this fine with--recursive --delete. The mirror will remain an exact replica.