Why not use Wikidata's Wikibase ? It seems to be exactly what we need: good internationalization method, good machine readability, support for the date datatype. The ability to add custom property could also make it possible to get an alternative to the badly inadequate category system. And of course, we could probably benefit from the many tools that are likely to be developed for Wikidata.
Topic on Talk:Requests for comment/Image information
I think use of wikibase is an excellent idea. Use of some database was discussed in one format or another for some years now. Use of wikibase properties was raised by User:Multichill at d:Wikidata:Project_chat#Wikidata_and_Commons.
+1