I’ve had a stab at a WordPress plugin for embedding Wikimedia URLs: https://github.com/samwilson/embed-wikimedia
It’s of course just a draft and proof-of-concept and beta and rough at the moment. It only supports Wikipedia and Wikimedia Commons; I’m going to add Wikidata next, I think, and then Wikisource (although that will mostly be a reformatted version of the Wikidata one, because all relevant metadata about Wikisource items is in Wikidata).
I have no idea if it’s very useful. I mainly want it for Commons photos, and Wikisource books.