Support for non-numeric grades

Are there any plans/work-in-progress to extend the Assignment and Grade services to include support for non-numeric grades (such as Pass/Fail or letter grades)?

I have drafted an extension and am keen to be consistent with any other work which is being done on this. I added the following section to the application/vnd.1EdTech.lis.v2.lineitem+json media type:

"gradingScheme": {
  "label": "My grading scheme",
  "description": "A simple pass/fail scheme",
  "items": [
    "Pass",
    "Fail"
  ]
},

The scoreMaximum property would not be required when a grading scheme is in use.

For the application/vnd.1EdTech.lis.v2.resultcontainer+json media type, the resultScore and resultMaximum properties would be replaced with a resultText property (of type string).

And for the application/vnd.1EdTech.lis.v1.score+json media type the scoreGiven and scoreMaximum properities would be replaced with a scoreText property (of type string).

I would welcome feedback on these changes. Thanks.