Ability to have Submitter or Assigned To person's department to be shown in the issue page

Allow a user to be assigned to more than one department. During implementation, it was explained to me that because we have users that do tasks for multiple departments, it would be more beneficial to use Projects instead. And then assign the users to multiple projects. I'd like to be able to use the department function instead of projects.

Ability to have members of a department assigned to tasks only if they belong to the same department as the Responsible Department.