Overwrite (only) desired properties of module through layered deployment

Question: Is it possible to only overwrite desired properties of a custom module without specifying the module (image name, createOptions, etc.) within the `$edgeAgent` block?

Info:
- iotedge version: 1.2.0

Our current deployment setup is that we have a basic deployment (priority 0) that contains basic settings for edgeAgent and edgeHub:
```json
{
"modulesContent": {
"$edgeAgent": {
"properties.desired": {
"modules": {},
"runtime": {
"settings": {
"minDockerVersion": "v1.25"
},
"type": "docker"
},
"schemaVersion": "1.0",
"systemModules": {
"edgeAgent": {
"settings": {
"image": "mcr.microsoft.com/azureiotedge-agent:1.2.0",
"createOptions": "{\"ExposedPorts\":{\"9600/tcp\":{}},\"HostConfig\":{\"Binds\":[\"/srv/edgeAgent:/storage\"],\"PortBindings\":{\"9600/tcp\":[{\"HostPort\":\"8082\"}]}}}"
},
"type": "docker",
"env": {
"UpstreamProtocol": {
"value": "AmqpWs"
},
"storageFolder": {
"value": "/storage"
},
"SendRuntimeQualityTelemetry": {
"value": "false"
},
"RuntimeLogLevel": {
"value": "verbose"
}
}
},
"edgeHub": {
"settings": {
"image": "mcr.microsoft.com/azureiotedge-hub:1.2.0",
"createOptions": "{\"ExposedPorts\":{\"9600/tcp\":{}},\"HostConfig\":{\"Binds\":[\"/srv/edgeHub:/storage\"],\"PortBindings\":{\"443/tcp\":[{\"HostPort\":\"443\"}],\"5671/tcp\":[{\"HostPort\":\"5671\"}],\"8883/tcp\":[{\"HostPort\":\"8883\"}],\"9600/tcp\":[{\"HostPort\":\"8081\"}]}}}"
},
"type": "docker",
"env": {
"UpstreamProtocol": {
"value": "AmqpWs"
},
"storageFolder": {
"value": "/storage"
}
},
"status": "running",
"restartPolicy": "always"
}
}
}
},
"$edgeHub": {
"properties.desired": {
"routes": {
"baseline-metrics": "FROM /messages/modules/baseline-metrics/* INTO $upstream"
},
"schemaVersion": "1.0",
"storeAndForwardConfiguration": {
"timeToLiveSecs": 7200
}
}
}
}
}
```

Additionally we have a use-case specific layered deployment (priority 10):
```json
{
"content": {
"modulesContent": {
"$edgeAgent": {
"properties.desired.modules.module-A": {
"settings": {
"image": "",
"createOptions": ""
},
"type": "docker",
"status": "running",
"restartPolicy": "always",
"version": "1.0"
},
"properties.desired.modules.module-B": {
"settings": {
"image": "",
"createOptions": ""
},
"type": "docker",
"status": "running",
"restartPolicy": "always",
"version": "1.0"
},
"properties.desired.modules.module-C": {
"settings": {
"image": "",
"createOptions": ""
},
"type": "docker",
"status": "running",
"restartPolicy": "always",
"version": "1.0"
}
},
"module-A": {
"properties.desired": {
"my-property": "my-value"
}
}
}
}
}
```

For specific use cases we want to overwrite the desired property `my-property` of `module-A` in a separate layered deployment (priority 100) **without** specifying the module (image name etc.) within the `$edgeAgent` block, similar to:
```json
{
"content": {
"modulesContent": {
"$edgeAgent": {},
"module-A": {
"properties.desired": {
"my-property": "use-another-value"
}
}
}
}
}
```

Can you please tell me if this is possible or how the deployment configuration has to be specified.