I'm pretty sure Rstudio uses this approach. The core app is all HTML/Javascript, but then they make a desktop version by putting a thin Qt wrapper around it and adding a few minor things like a relevant menu bar.
That sounds a neat way to still provides a comfortable user experience whilst working on languages not easily embeddable in the browser.
Indeed, especially with PyQt. The problem is that your binaries can easily be huge on Mac/Win.
Well we can imagine choosing a version statically linked or a dynamically linked one when dowloading ? I agree it isn't a really slick solution, but it's a tool for developers it won't hit too hard the entry barrier.