Once upon a time, I did some work to investigate putting Parrot into Emacs, and then writing an Elisp implementation of Parrot. I had some promising early results, but the complaints about Guile community being "too small" to handle the load of Emacs' needs probably applies to Parrot as well.
I've admittedly never been fully convinced at RMS' claim that we could compile all other languages down to Guile. I have a master's degree specifically focusing on multi-lingual VMs, and I'm somewhat convinced this is all much harder than it looks.
If I were going to approach this problem anew, I'd see if it's possible to embed Vert.x in Emacs and write an Elisp implementation for Vert.x.
Christopher Allan Webber, Evan Prodromou likes this.
Just realized, sadly: Vert.x switched to the EPL instead of the Apache license, so my idea is a non-starter for licensing reasons.
I definitely think it will be hard, and I'm also pretty skeptical of the idea that all languages can compile down to Guile. I'd love to see it be true! But thus far, it seems that it's been hard to have that happen.
But I think emacs lisp -> guile (or Parrot, for that matter) may be different: there's only one source that uses emacs lisp, which is emacs, and it seems pretty likely that collaborating upstream with emacs would make this possible.
Given that and how much works, and given the things that don't or aren't ideal, it seems like the hurdles remaining aren't impassable.