I work at Human Made (owner of the above repo, and an enterprise WordPress agency), and we run all our sites on an all-AWS stack. We have a few other plugins for related AWS pieces, including email via SES [1] and a dynamic image thumbnail generator that runs on Lambda [2] that might also be relevant.

Using S3 for the uploads solves our problems without needing EFS, as we disable file system changes through other methods. Plugin installs or upgrades are great, but aren't tracked in the git repo, so we do those via local upgrades and deploy out to AWS instead.

The article also mentions installing WordPress as being a pain, but you can easily automate this using wp-cli [3] if you want to. Your RDS containing the WP data is going to be shared though, so there's no real need to install more than once.

[1]: https://github.com/humanmade/aws-ses-wp-mail [2]: https://github.com/humanmade/node-tachyon [3]: http://wp-cli.org/