That said, I never had issues with certbot on Arch Linux, and I have been using it for a really long time.
Since Arch Linux is bleeding-edge, it does not diverge from latest version. :D
I can see the use in a tool that will scan all certificates configured in local web servers and monitors for close expiration dates, though. Not just Let's Encrypt, but also any other ACME accounts and certificate directories you may need. The biggest challenge would probably be dealing with encrypted certificate files, and after that getting email set up correctly. Nobody seems to have made it because it's so easy to script or add to a pre-existing monitoring system, so this could be a fun open source project. You probably can't use the letsencrypt brand name, though.