You need a network file system that supports symbolic links.
You can add mfsymlinks to your CIFS mount options on each server to enable virtual symlink support for Windows-backed CIFS shares. (These symlinks will work on other Linux systems with this mount option enabled, and on Macs, but they will appear as files when viewed from Windows computers.)
You could also use a Unix-backed CIFS share with the CIFS Unix extensions, or NFS, or anything else that supports symbolic links.
I cannot speak as to how Certbot will behave if two instances running on different machines try to access e.g. cli.ini concurrently, however.