Someone's already made plugins that embed a Neovim instance right inside VSCode[1] and Sublime Text[2]. There's no emulation here, just straight up neovim running behind those buffers. I've tried VSCode with that plugin (though personally I like to stick to just neovim when I can), and I can say that despite some minor bugs it's been a pretty smooth experience. Even stuff like `gt` to change editor tabs is supported.
[0]: https://neovim.io/
Why would an app like this require a subscription and not a one off payment.
I think many small developers are taking cue from large enterprises on how to price products without thinking it through. There was another similar discussion about a YC macOS notification widget company the other day.