During discussions about language detection (T118278) and the TextCat Demo (T134427), someone suggested either modifying the existing TextCat demo or creating a new demo that would allow people to experience some of the UI options for language ID/cross-wiki searching.
The demo would have to provide some examples of queries for different use cases (good language detection, bad language detection, multiple language ambiguity, etc.) as well as allow users to try their own queries.
There are still some open questions about what wikis to include, what languages to include, and how many UI variants (and which ones) to include.
The alternative is just to stick with the mockups (T136639) for now.