Ultimately, putting a Varnish cache seemed like the only logical answer to speed things a bit more, but that didn't avoid Wordpress security attacks.
For fun though, I built an experimental wordpress-clone dashboard that saved Hugo-compatible files instead, so I wouldn't miss Wordpress' editing features. The result was superb (<5 seconds to regenerate the ~1000 articles blog), but I missed the Wordpress plugins too much to switch to Hugo entirely.
But I still agree with you: "keep wordpress' editing experience, but generate static sites" is a pretty promising direction IMO.