At the time of this writing I had not found anyone that was able to provide a solution for updating a Deployment Name or Description from vRO during a Subscription Event. The only method was to update __deploymentName prior to submitting the form. Any changes to __deploymentName from the subscriptions events such as Requested, MachineBuild, or later have no effect.
I explored all the Request and Resource APIs but could only view the name and description. There is no API listed for updating a resource. Or at least no documented API 
While running Fiddler and using the UI to update the Deployment Name i found that there is an obscure, and as far as I know undocumented, API with a uri of /consumer/deployments.
I was successfully able to use this uri to update the Deployment Name (and description if desired) from the MachineBuild subscription event. It will likely work just about anytime because I initially got it working in a test workflow completely outside of any Subscription Lifecycle event altogether. I should also mention we are on vRA 7.6, but I suspect it will work from earlier versions of 7.x.
Here is the code I'm using during the MachineBuild state to append the machine name to the deployment name:
System.log("*");
System.log("Updating Deployment Name");
System.log("********************************************************************************");
try{
var correlationId = System.getContext().getParameter("__asd_correlationId");
var deployment = getDeploymentResourceByRequestId(correlationId)
if (deployment){
var resourceId = deployment.id;
// System.log(res.id);
// System.log(res.name);
// System.log(res.dateCreated);
var deploymentName = deployment.name;
var newDeploymentName = deploymentName;
System.log("-- Current Deployment Name is " + deploymentName);
var pos = deploymentName.lastIndexOf("-");
if (pos > 0){
newDeploymentName = deploymentName.substring(0, pos).trim();
}
newDeploymentName = newDeploymentName + " - " + assignedServerName;
System.log("-- New Deployment Name is " + newDeploymentName);
try{
setDeploymentName(resourceId, newDeploymentName);
}catch(e){
System.log("-- Failed to update deployment name: " + e);
}
}
}catch(e){
//don't raise error just because we couldn't update the deployment name....
System.log("-- An unexpected error occurred while updating the Deployment Name: " + e);
}
//////////////////////
// Helper Functions //
//////////////////////
function setDeploymentName(resourceId, name){
var cafeHost = vCACCAFEHostManager.getDefaultHostForTenant()
//Create the rest client for the targeted tenant
restClient = cafeHost.createRestClient("com.vmware.csp.core.cafe.catalog.api");
//Uncomment to view the API URL used by the client
//System.log(restClient.getUrl());
var props = new Properties();
props.put("name", name);
//We can also update the description by adding it here
//props.put("description", "This blueprint offers the most flexibility in defining a Windows Server build at the cost of completing the most complex request form.");
var response = restClient.put("/consumer/deployments/" + resourceId, props);
// System.log(response);
}
function getDeploymentResourceByRequestId(requestId){
var cafeHost = vCACCAFEHostManager.getDefaultHostForTenant()
var requestService = cafeHost.createCatalogClient().getCatalogConsumerRequestService();
var deploymentResource = null;
try{
var results = requestService.getResourcesProvisionedByRequest(requestId);
//retrieve the results
var resources = results.getContent();
//Loop through the resources until we find the Deployment resource
for (var i in resources){
// System.log(resources[i].id);
// System.log(resources[i].name);
// System.log(resources[i].requestId);
// System.log(resources[i].resourceTypeRef.getLabel());
// System.log("==============================");
if (resources[i].resourceTypeRef.getLabel() == "Deployment"){
deploymentResource = resources[i];
break;
}
}
}catch(e){
System.log("-- Failed to get deployment resource");
}
return deploymentResource;
}
