It would be very usefull (for migration from dist-for for example) to be able to (easily) copy artifacts from one workspace to another inside workflow.

Whilst you could work around this with artifacts this has several short comings
1) artifacts are available to users with permissions and you may want to generate a secret file.
2) having to copy lots of artifacts will pollute the artifact list and will make it harder for users to see the actual artifact.
3) there is a larger chance of collision with artifact names.