I actually have a need for something like this. I wrote a single-user flashcard app which supports multi-device sync. The way I sync is having each device write to its own journal file a list of commands, such as "create card" or "update card with ID 1234" or "insert card evaluation". To "sync", each device just pushes up its journal to a common file store and pulls down each other device's journals. Then it just plays back all the edits in timestamp order. (It works fine for single-user since you're very unlikely to be using two devices at the exact same time.)

Anyway, I never did end up implementing an optimal "update card with ID 1234". If you edit a flashcard's front text, instead of updating the front text field alone, I ended up just writing out an entirely new copy of the flashcard in the journal (with the ID 1234 encoded). Super inefficient.

I was toying with the idea of coming up with a simpler format that does basically what this JSON patch does, where you an just encode "update object 1234's field foo.bar.baz to string ABC".

I figured I'd only need a handful of operations, to insert a new object, replace a node in an object's property tree given a key path, delete an object, append to an array property, etc.

If anyone has other solutions other than JSON Patch, I'd love to hear about them.