This is a wonderful idea, actually; developer conveys info that a mix of brand, builder and other similar tags wouldn’t. Clearly it’s such a natural thing that it’s been slowly mapped for more than a decade now.
Besides, services built atop OSM could actually use the data here to advertise the use of themselves in place of commercial mapping providers, which is a boost to our ecosystem!
My concern should be clarity on the value of the tag.
The talk page on the wiki discusses special-purpose vehicles — companies built by and for just one or a few real estate projects — to shield the parent company from legal liability.
What about subsidiaries? One of the biggest companies on the Philippine Stock Exchange is Vista Land and Lifescapes Inc (VLL), which, if you search for Vista on the taginfo page for developer keys, reveals zero results.
Meanwhile, one of its many subsidiaries, Camella Inc., reveals 11 results specifically under its trade name developer=Camella Homes, which takes up the vast majority of all developer=* uses here in the Philippines!
The proposal page should clarify IMO:
should the value be names of holding companies (like Vista Land [and Lifescapes] with 0 uses; or Ayala Land with 2 uses),
or that of subsidiaries, which in my experience are the consumer-facing names (like Camella Homes with 11 uses and Avida Land with 1 use)?
Additionally, I’d also like some discussion on a similar tag which would be very helpful to the goal of classifying development projects: developer:wikidata=* with 301 uses.
If that would be added to this proposal, I’d love it better.