CCing from commons, please participate there as this will be a cross-wiki shared feature
During the last hackathon I created a new on-wiki tabular storage described in T120452, similar to CSV and TSV formats. It allows any user to create a page, e.g. "Data:List of interesting facts.tabular" (demo), and keep it as a table, rather than wiki text. Tabular storage allows strings, numbers, Booleans (true/false), and "localized strings" – a string that has different value depending on the language. Additionally, tabular data stores metadata, such as description (localized) and license. More metadata can be added as needed.
Tabular storage greatly simplifies storing data for lists, tables, and graphs. Graphs may directly access tabular data, and on-wiki tables and lists can be created by using simple Lua scripts. This storage is fundamentally different from Wikidata, because it works with "blobs" (batches) of data, whereas Wikidata works with tiny "facts". Wikidata technology is simply not suited for large storage such as the list of the most expensive paintings, the shoe size comparisons table, or data to plot Moscow subway growth.
After a long discussion, it seems Commons is the best fit for such data. Commons community already has good experience with international multi-licensed content. The current proposal is to create the data namespace on Commons, and use it from all of the wikis.
Feel free to experiment with it at http://data.wmflabs.org/wiki/Data:Sample.tabular. Note that you can view it with different languages, e.g. http://data.wmflabs.org/wiki/Data:Sample.tabular?uselang=fr
Technical notes: When storing, the data is validated and stored as JSON, so there are no delimeter problems common to the traditional CSV/TSV files. At this point, the wiki editor shows tabular data as a JSON, but very soon I hope to have a CSV/TSV editor to simplify copy/pasting, and afterwards – a full scale spreadsheet table editor. Eventually, I would also like to implement Q number support, allowing direct links to Wikidata.