Hoi,
Another broken record. I understand how identifiers added to an item make for the item and an external record to be the same. This is helpful because it allows comparison of the statements between Wikidata and the external source.
What is the benefit of Schema.org. Why have it how will it help us.
Or to give you an example. I propose to link red links and wiki links in all Wikipedias to Wikidata items. It allows for an improved quality in the Wikipedias in a similar way as the interwiki links brought more quality. It will also add items to the lists of items that have no article based on queries from Wikidata (a benefit to projects like women in red). It will make it easier to add the sources from DBpedia to Wikidata based on the statements in Wikidata.
So what is the benefit from your proposal? Stating that it will in the abstract does not give me a warm feeling.