Change Management- WI Management

Hi,
 I have 2 questions on WI Management here.

1.  While making a work item approval, can i define a particular role (and add users in to that role)  who can approve the WI.
Note: Similar functionality is available when you do along with change set. i,e Require a work item with resolved approvals when a change set is delivered.
But here i am looking for if a project is using only WI Management not source code.

2.   While adding Approvers in Approval tab,  All users gets shown in the "select users" popup box, which is not a good idea what i feel.  How can i display only the people who are in that particular project area . Currently it displayed all the users who have been added in that JTS server.