OK, so more and more C++/native stuff... Why not make a fully C++/native app? I don't see anything special in the UIs of Atom, VSCode, Bracket or whatever that is really hard to implement natively. It might be somewhat harder, but it is worth it.
Web developer-efficient... But when this goes against the end-user efficiency, I'd prefer the latter one.
SublimeText is written in C++ with the Skia library [1]
It exposes an ABI that you can consume via Python scripts.