We also have this requirement, using variables as content for the node label. The NodeLabel parameter plugin is not a solution as it also doesn't allow the use of variables as the default parameter value, the string entered has to match an existing node name.
Plus one vote for this option from my side. I have jenkins swarm slaves in Docker ran dynamically and I need some functional to send build to exact node started for it. Using variables in node label would be really helpful in this task.