>you could put together anything from a simple test/editing environment to a full-blown IDE.
People already do this with Emacs.
As someone who switched a few weeks ago, I would find that a much more intriguing breadcrumb trail.
Exactly this. I had used Emacs for many, many years and finally decided to give Vim a go... and never looked back. Emacs is very powerful, and while the Elisp infrastructure has distinct advantages over Vimscript, the compositional richness of Vim's editing model is amazing. I don't have to drop to scripting because Vim gives me the power I need more quickly and easily.
But it was becoming clear that something else was going on with modern vim, so after testing the waters a bit for my needs, I decided to go all-in as much as an ecosystem research project as anything else.