The objective is to improve the usefulness of the other projects and thereby increase their traffic. That is, more articles and books are read, more pictures are seen and downloaded.
Lets pick one language, Yoruba, as an example. There are currently 32,624 pages in its Wikipedia. There are some 40 million people speaking the language. So what can we do for Yoruba editors and readers. How can we track what makes a difference and also what makes a difference and what can the WMF do to achieve this.
* We can improve list support.
Currently the best support for supporting lists in a Wikipedia is "Listeria". It is supported by Magnus.. Listeria lists have been shown to be more up to date then manual lists on English Wikipedia, for less resourced projects this will be even more true. When existing lists can be easily included in an article, it will expand available information hugely.. Here an example of Listeria lists on the Yoruba Wikipedia. Content of these lists show in Yoruba. Lists are better supported and adopted when it is WMF supported functionality.
* Choosing pictures for illustration
When people look for a picture, they have to goto Commons or they visit Wikipedia articles on the same subject and use these same pictures. When the Special:MediaSearch is available as a tool from every Wikipedia article, a much richer palette of pictures becomes available to choose from. (The search is for "Agbègbè Ìjọba Ìbílẹ̀ Mushin")..
The cool thing is, when this tool is available when writing an article, it is easy to more pro-actively add labels to Wikidata. This will improve the performance for the Special:MediaSearch even more.
What would truly support Special:MediaSearch is disambiguation. It is unreasonable to expect that we get descriptions in all the 300+ languages we support. What Reasonator supports are automated descriptions. It makes it easy and obvious to choose the right item in any language.
For the Wikimedia Foundation to support other languages, for it to move the needle on any and all languages, we need to measure what is meaningful. The number of searches by Special:MediaSearch and what language was used. The number of pictures used in each Wikipedia. The effect lists have on the writing of new articles.
When we did not measure such numbers so far, it is what we should do to move the needle. One needle is the total number of reads quite another is the number of reads for each project. Same for the use of Wikidata and Commons.