It's a pity IMHO that this interesting implementation of JSON objects into wikicode has - apparently - so a limited scope; I hope, that it can be generalyzed to any JSON data structure and that the resulting extension is merged with the Scribunto function mw.loadData() so that the same data could be read by extension, by js and by Lua. Perhaps, a dedicated Data namespace could be useful in future.
Topic on Extension talk:TemplateData
About the new namespace, see bugzilla:50512.