BFS (the BeOS File System) had very cool features, especially for the time (see https://arstechnica.com/information-technology/2018/07/the-b...):

- 64-bit, journaled, UTF-8 capable, extended attributes: things that are standard today but novel at the time

- It had "live queries" meaning feeds into file changes. AFAIK only NTFS has that today with https://en.wikipedia.org/wiki/USN_Journal. Inotify is a hack: have you tried monitoring your root folder ?