JSON Patch

I'm probably missing a use case here, but with the JSON Pointer spec they use feeling so "URL-y", couldn't you skip the whole meta-json syntax? So rather than doing

    HTTP/1.1 PATCH /user
    Content-Type: application/json-patch+json

    [
      {
        "op": "replace",
        "path": "/username",
        "value": "bob"
      }
    ]

why not

    HTTP/1.1 PATCH /user/username
    Content-Type: application/json

    "bob"

I feel like you could pretty sensibly implement replace/delete/append with that.

Edit: "test" and "copy" from the json patch spec are unique! So there is those, as well as doing multiple edits all at once in a sort of "transaction".