It would be nice to be able to copy artifacts from another job's workspace instead of archived artifacts only.
This could be achieved by adding a selection "workspace" to the combo box "which build".

Why? Imagine this situation:

• Job A builds a Java project
• Job B builds large data (some GB)
• Job C copies artifacts from A and B and creates the completed build

Now, archiving some GB of artifacts in B takes a lot of time. Maybe you only need the workspace, for Job C anyway copies B's results and archives the artifacts of the whole build again.

So, if C could copy B's workspace, we could save the time for archiving artifacts in B.

An alternative would be the plugin "Clone workspace SCM", but this prevents the use of a real SCM in the same job and is less convenient in some cases.