I've created a prototype of the proposed idea:
https://people.wikimedia.org/~jdrewniak/collapsed-languages/index.html
This page features the proposed collapsed language menu.
- The button text is only in english for now (but we hope to translate this).
- Ctrl+f works
- On mobile the links expand inline, instead of in a modal.
- non-js browsers are given the current layout
I hope this prototype give people a clear vision of the idea, and a chance to see what it looks like 'for real'.