We are implementing Plone as a document management system in a hospital setting. In doing so, the review process asks for two review steps:
There may be an easier way to approach this.
Plone workflows can be stacked; e.g. you can assign more than one workflow to a content type.
This means you can assign both a nurse and a doctor workflow, each handing out specific permissions. If you set up your roles correctly per workflow, your use-case should be easy to implement; just split Roles into those for nurses and doctors.
So, where a default workflow uses Reviewer, Editor, Contributor, Member, etc, use DoctorReviewer, NurseReviewer, DoctorEditor, NurseEditor, etc. That way the two workflows will handle two sets of parallel permissions, transitions and states.
I do not know enough about your use-cases if this will solve your problems at all, but I just wanted to make sure you knew about the option before exploring complex custom plugins.