I think you can use the new "quantize" transform here.. something like:

transform: {
    "type": "gpii.transformer.quantize",
    "inputPath": "display.screenEnhancement.fontSize",
    "ranges": [
        {
            "upperBound": 24,
            "output": "small"
        }, {
            "upperBound": 32,
            "output": "medium"
        }, {
            "upperBound": 42,
            "output": "veryLarge"
        }, {
            "output": "huge"
        }
    ]
}