In our company one end-user may perform tasks for more than one department. Each department likes to be able to view their open helpdesk tickets. Therefore rather than mapping each user to a department we have implemented an additional incident request field called "Benefiting Department" that the end-user has to choose when they make a request. That way the user chooses which department will "own" the ticket. We then report on a regular basis to each department based on the "Benefits Department" field.

This works reasonably well in terms of incident requests but it has made use of the service catalog difficult. 

What I need is either for the user to be able to choose the department that owns the service request at the time they make the request (and thereby allowing all the various features associated with departments to work correctly) or I need some way of having an additional field that is shared between all templates (service requests and incidents) that in the database is the same field so that I can use it for reporting and also in views.