Installing WinFsp and SSHFS-Win for this feature uses roughly 7 MB of disk space; it is way overkill just to download two files and still requires all the tens of thousands of developers to write or find their own script manually.
I will ask the following question to heed your advice to move in the direction of a fully-specified idea:
How about Let's Encrypt or Certbot supplying everyone with an optional script to download the cert files (for each kind of OS), and Acme and/or Certbot sends the development website a renewal time notice (by calling--doing a POST or GET--to a PHP or other URL in the dev website from the Certbot process)? Then all the developer has to do during setup is download the script. The Acme process would then indirectly cause the local script to download the cert files. This requires no direct secure connection from the Certbot process to the development server, and only the work of writing the script for every OS added (optionally) to every Acme provider, in addition to supporting the renewal notifications.