I do like to deduplicate my BitTorrent downloads/seeding directory with my media directories so I can edit metadata to my heart's content while still seeding forever without having to incur 2x storage usage. I tune the `recordsize` to 1MiB so it has vastly fewer blocks to keep track of compared to the default 128K, at the cost of any modification wasting very slightly more space. Really not a big deal though when talking about multi-gibibyte media containers, multi-megapixel art embeds, etc.
Have you considered "reflinks"? Supported as of [OpenZFS 2.2](https://github.com/openzfs/zfs/pull/13392).
Haven't used them yet myself but seems like a nice use case for things like minor metadata changes to media files. The bulk of the file is shared and only the delta between the two are saved.