This will require having all references stored in the database as well as creating reference identity and deduplicating references. I think we don't have anything like that do we? This is a way larger piece of work than all the rest of the requirements which could be implemented just by parsing the articles.
Topic on Talk:Core Platform Team/Initiatives/References API
As far as I know, this is what the Shared Citations proposal by @LWyatt (WMF) is about.