How about building an "Affinity Gallery Manager"?
On the photo editing mode, you have the technology / libs for such a tool.
It could offer Lightroom like "Affintity Photo-lite" quick retouching tools, cropping, etc, and could open in Affinity Photo seamlessly for more detailed changes.
But most importantly it will allow collecting, and cataloguing one's photos, share non-destructive versions of photos in different project folders, organizing and searching (by date, tag, score, metadata, location, etc), batch exporting for clients or web upload, etc.
Perhaps it could also work for cataloguing vector (Affinity Designer) images, and maybe Publisher files too.
Such a tool is needed, and Adobe and/or Capture One has the near monopoly.
