The author of the new file-based block cloning code had this in mind. A backround process would scan files and identify dupes, delete the dupes and replace them

The author of the new file-based block cloning code had this in mind. A backround process would scan files and identify dupes, delete the dupes and replace them with cloned versions. There are of course edge cases to consider to avoid data loss, but I imagine it might come soon, either officially or as a third-party tool.