The special page should somehow show which pages on the site are linked to an
item. Preferably this should be done in such a way as to make it easy and
efficient to create new items for missing ones.
The special page could also do an additional pass to check if the items are
"complete" given the existing sitelinks in the items and the langlinks in the
pages. This could imply that the query to the Wikidata api would use additional keywords in "props" to include additional entries from the page_props table, that is the wbgetentities must be updated.