While doing some more reading about this area, I stumbled across this wonderful comment originally posted as a response to Miguel de Icaza's 2012 article "What Killed the Linux Desktop) that was preserved on Hacker News (https://news.ycombinator.com/item?id=13573373). To summarize, perhaps the Linux desktop would have been more competitive if it promoted an OpenDoc-style component-based GUI that fits with the Unix philosophy and is more amenable to the development patterns of free and open-source software, rather than trying to compete head-on against Windows and macOS by adopting Windows-esque and macOS-esque GUIs. This resonated with me.
I believe that despite the much discussed notion that desktop computing is waning in influence as smartphones and tablets became popular, there is still room for a workstation-quality operating system that allows us to flexibly customize our workflows, and that a Smalltalk or Lisp base combined with an OpenDoc-like API would be an excellent platform to facilitate such a platform. I would be very interested in working on such a project, but coming from a Unix systems software research background, I'm still familiarizing myself with the body of work on Smalltalk, Lisp machines, and OpenDoc.
You should look into Plan9. I think it fits that description in some ways. (Disclaimer: I've never used Plan9 before)
Seems that way, check that with showdead on.
In terms of linking to reposts, see https://news.ycombinator.com/item?id=16344002 to avoid kerfuffles in the future.