Hi all,
I just subscribed to this list, after it was mentioned to me. I'd like to give a brief overview of what I can offer in terms of WLM and Wikidata. I skimmed the July mailing list archive about Wikidata, but please forgive me if I repeat something already said.
Last year, I wrote the official WLM tool for the UK. As part of that exercise, I also created Wikidata items for all grade I and II* monuments in the UK on Wikidata.
As a "side effect", I also created a tool to browse any monument with an ID number on Wikidata:
https://tools.wmflabs.org/wlmuk/index_wd.htmlI do not consider this "production grade" at the moment, but it could be seen as a prototype. And while it currently requires a country-specific property (or multiple), it could be extended to also use anything with P1435 ("heritage status") within a country. That would abolish the need for unique, stable IDs, though it will make management of these objects a little harder of Wikidata.
As for syncing with Wikipedia(s), I can offer a list-generating and -updating bot already in in production on English Wikipedia and Wikidata, as described here:
http://magnusmanske.de/wordpress/?p=301This could be used as an automated to-do-list (e.g. a list of all monuments in Lower Saxony without an image on Wikidata), or a total overview of these items (with image where available). This will require an image to be set in the Wikidata item, and it will only show one image, so it might not be suited as a show-the-latest-image-of-X, and it will not search Commons on its own.
For synchronizing a list of monuments with Wikidata, I can offer my trusty mix'n'match tool:
https://tools.wmflabs.org/mix-n-match/I can upload any list that consists of names and IDs (which can be fake), optionally a brief description and a URL (pointing to an external catalog). The tool offers various ways to match entries to existing Wikidata items, or declare entries as "not on Wikidata yet", so they can be batch-created.
For a set of items, it can scan Wikipedia (and other projects) for images, and present them for one-click addition to Wikidata. It can even do Commons free text search, though there tend to be quite a few false positives. At the very least, this could be a "from home" activity for WLM enthusiasts.
A missing piece in this "ecosystem" appears to be a Commons-scanning bot that looks at recent WLM uploads, and recognizes IDs of monuments, or maybe just names, and generates a list of suggested matches between Commons and Wikidata (and, optionally, Wikipedia). Such a bot could surely be arranged, given detailed enough specifications.
While I can not promise to devote as much time as last year on this, I'll help where I can. One point I would like to emphasize is that, whatever we come up with, I would like it to be generic enough to work for all, or at least most, sets of monuments, or even beyond that; every set of items with coordinates and/or "in admin unit" property should work out-of-the-box, and some parts (e.g. WD-FIST, Listeria) already work fine for biographies, taxons, etc.