My team is considering a bid for developing a site for a large US based NGO. We've worked on large CMS build-outs before using Drupal but aren't really excited about using it again. We recently built a large site using the WordPress REST API consumed by a Nodejs front-end and were pleasantly surprised with process and results. It provided the client with a consistent interface for editing content and us with decent, modern, testable front-end tooling. Curious to hear fellow HN readers experiences with this domain & similar tooling.
Also worth mentioning, I poked around the 18f.gsa.gov site to see if there were any similar projects but didn't see anything. I saw a reference to Federalist but no links. From the description it sounds Jekyll-esqe so might not be flexible enough for our needs.