You can only map to account names, not IDs. The only way you could "fake" it would be to create an enumerated property in the property dictionary, where the name field would be the ID, and the value field would be the name that you wanted to map to. Then map to that using Server properties. It's kind of backwards and would require you still knowing which IDs go with each account name. So in short, just stick with mapping to names.
And it’s actually mapping the bladelogic role:user to a local account. not a display name to a uid.