Currently, workflow states as well as workflow actions are declared as part of the skin (i.e. both are declared in files which are located in the skin's "workflow" directory. For actions, this is very well as actions should be able to change for different skins. But workflow states are stable over all skins as they work firmly together with the code (workflow models), so workflow states should be declared in the plugin descriptor.
We should have a plugin item builder "WorkflowState" which brings in a new workflow state with the same data as currently in the workflow states file.