Add a Note section to project member visible to project administrators. Have this Note section be able to be pulled as a report so that it can act a project directory for the team (but more helpful, with the notes).
Please note that Roles within the system is tied to permission and our company has simplified these for ease of project set-up. Subcontractors especially, get lumped together and teams would like to identify the PMs, foremen, vs. leadmen or supplemental/back-up members.