Hi @JDrewniak (WMF) - as discussed offline earlier, I agree with concept but did have concerns with the open 'drawer' of languages being disconnected from the "more languages" button (the search box comes up in between the two).
It is unexpected behaviour (initially when trying the demo I thought it was actually just scrolling browser window down to the extra languages) and also looks strange with the callout arrow appearing over the search bar.
Secondly, while styling the more languages looking like the other main languages around the globe fits well visually, it seems misrepresentative because it is actually a toggle button and not like the other language links around it.
I created a quick animated gif showing the button placement below the search instead, updated the visual style as well and added an animation sliding open of the more languages which makes the transition more overt.