Yeah, in general (a bit of a tangent), ideas from Plan 9 are really powerful. For example, the Acme text editor exposes it's API as a file system (it's represented via Unix sockets in plan9port, but FUSE is available as well there). It's easy to write scripts to manipulate the editor, and quite fun.
I 100% have been inspired plan9, not actually a tangent at all!
I never spent much time in Acme. I did use wmii as a daily driver window manager for a number of years, which was also 9p based! I wasn't great at scripting it, and the docs have always been basically non-existent for it's 9p interfaces... but I did poke around and look at things, which was super easy to do because it was just a filesystem! I did find this short example of some wmii examples, inside a Chicken Scheme 9p write-up, which is lovely to see online: https://wiki.call-cc.org/eggref/5/9p#utility-procedures
It's a fine distinction, but I do like json2dir and my own work a bit more than 9p because with apps that expose 9p, if the app goes away, so does the filesystem! 9p is an interface to talk to some process state. But if you just keep state on the regular filesystem, it will stick around & persist beyond the life of the process. The downside is your app needs to watch for that state changing, needs to be able to reconcile changes as they happen. On the upside though, now you can use a lot of great filesystem utilities: for example btrfs or zfs snapshots or incremental-backups are going to work as usual!
Being able to easily script your world is-I think- a missing key to unlocking personal computing. Different technologies discussed, but another serendipitous thread on personal computing from today: https://news.ycombinator.com/item?id=44837783