Isn’t this VS Code with the Vim extension?
Intriguing idea, though not sure how viable.
But the actual core editor is all seperate, written in ReasonML (or OCaml if you know that instead), with a bunch of C libs in the background we've wrapped (Skia/Harfbuzz/We wrap real vim etc).
So the core editing experience has no code sharing, but the extension side of things does!