I think you will need to write your own mapping. If you download a material JSON from the Editor, you can see the properties and formats are different (eg look at the diffuse color attribute:
{
"ambient": [0, 0, 0],
"ambientTint": false,
"aoMapChannel": "r",
"aoMapUv": 0,
"aoMapTiling": [1, 1],
"aoMapOffset": [0, 0],
"diffuse": [1, 1, 1],
"diffuseMapChannel": "rgb",
"diffuseMapUv": 0,
"diffuseMapTiling": [1, 1],
"diffuseMapOffset": [0, 0],
"specular": [0.23, 0.23, 0.23],
"specularMapChannel": "rgb",
"specularMapUv": 0,
"specularMapTiling": [1, 1],
"specularMapOffset": [0, 0],
"specularAntialias": true,
"occludeSpecular": 1,
"useMetalness": false,
"metalness": 1,
"metalnessMapChannel": "r",
"metalnessMapUv": 0,
"metalnessMapTiling": [1, 1],
"metalnessMapOffset": [0, 0],
"conserveEnergy": true,
"shininess": 32,
"glossMapChannel": "r",
"glossMapUv": 0,
"glossMapTiling": [1, 1],
"glossMapOffset": [0, 0],
"fresnelModel": 0,
"emissive": [0, 0, 0],
"emissiveMapChannel": "rgb",
"emissiveMapUv": 0,
"emissiveMapTiling": [1, 1],
"emissiveMapOffset": [0, 0],
"emissiveIntensity": 1,
"normalMapTiling": [1, 1],
"normalMapOffset": [0, 0],
"normalMapUv": 0,
"bumpMapFactor": 1,
"heightMapChannel": "r",
"heightMapUv": 0,
"heightMapTiling": [1, 1],
"heightMapOffset": [0, 0],
"heightMapFactor": 1,
"alphaToCoverage": false,
"alphaTest": 0,
"opacity": 1,
"opacityMapChannel": "r",
"opacityMapUv": 0,
"opacityMapTiling": [1, 1],
"opacityMapOffset": [0, 0],
"reflectivity": 1,
"refraction": 0,
"refractionIndex": 0.6666666666666666,
"cubeMapProjection": 0,
"cubeMapProjectionBox": {
"center": [0, 0, 0],
"halfExtents": [0.5, 0.5, 0.5]
},
"lightMapChannel": "rgb",
"lightMapUv": 1,
"lightMapTiling": [1, 1],
"lightMapOffset": [0, 0],
"depthTest": true,
"depthWrite": true,
"cull": 1,
"blendType": 3,
"shader": "blinn",
"useFog": true,
"useLighting": true,
"useSkybox": true,
"useGammaTonemap": true,
"aoMapVertexColor": false,
"diffuseMapVertexColor": false,
"emissiveMapVertexColor": false,
"specularMapVertexColor": false,
"metalnessMapVertexColor": false,
"opacityMapVertexColor": false,
"glossMapVertexColor": false,
"lightMapVertexColor": false,
"diffuseMapTint": false,
"specularMapTint": false,
"emissiveMapTint": false,
"metalnessMapTint": false,
"mapping_format": "path"
}