How do I change the values in the "Status" drop-down list in a case?

I've been checking thru a lot of the past threads and couldn't find any conclusive answer on the following scenario with regards to case management workflow:

I want to re-design our companies support case workflow based on the role of the user logged in.

As a simple example, if our company uses Tier 1 support person role, Tier 2 support person role, and Tier 3 support person role, I want the "Status" field to be loaded only with the values based on the role of the user. (I also want the "Assigned To" field to be loaded based on the role too.)

if I'm a Tier 1 support person, then when I create and/or edit a case, I only want "Opened", "Closed", "On Hold" as available statuses in the case.  I also want the Tier 1 support person to have a limited number of people and groups to whom they can assign the case using the field "Assigned To", such as Tier 2 group.