Watchlist contacts on service desk tickets.

It would be convenient if the customer contact list were available as a menu in the watchlist field.  That is: you could add people from your customer base, or manually add someone.  We have an organization that has over 500 employees.  Our service desk is set up so that our employees are our customers.  The employee submits a helpdesk incident and we would like our technicians to add the supervisor to the incident.  It would be nice if they could select the supervisor from the list of customers instead of typing the name each time in the watchlist.  As it stands right now, I have set up a trigger using custom fields that adds the supervisor to the incident but there is no way to add the supervisor to the watchlist except manually.