Hi Gerard,
I mostly agree with you. However, I disagree with this:
This proof of concept is largely based on existing WMF functionality so it takes very little for the Wikimedia Foundation to adopt the code, do it properly particularly for the Internationalisation.
Turning prototype code into production code is never trivial. When you’re writing a prototype, you get to skip all performance and edge case concerns, and you don’t need to integrate it into existing code, you’re just interested in getting something working. I hope (and expect) that the WMF will make improvements to Commons’ multilingual search in the future, but it’s definitely not a “very little” amount of work that needs doing, it’s a year or more worth of developer time.
Thanks, Mike