As we say down here in the South, that’s a big’un. I don’t know if your sites are huge, but if they are, I would recommend setting up a permanent and updated lite version of your site that you can use to clone and run regression tests against. I wrote up how to do this recently and you may find it helpful.
So plug those into your .circleci setup and see if you can get it working. You may need to pump in some environment variables into your CircleCI project. Mine has ADMIN_EMAIL, ADMIN_PASSWORD, GITHUB_TOKEN, GIT_EMAIL, TERMINUS_SITE, TERMINUS_TOKEN, and TEST_SITE_NAME.
You are welcome to use that Orb or copy/paste its contents into your own Circle yml. I’ve been collaborating with Faux Al Gore in order to get comfortable with the conventions and release procedures before I use them on Pantheon’s official orb.