Support of Special User look ups in report filtering.

Currently when trying to build a report on the Case Object and use the Case owner we are not allowed to use this in the filters. This is because the Case Owner is a user look up but also a queue. Right now we only support user look ups that id field is a reference to User / Account / CustomerInfo / SurveryQuestion object or GSRelationship object. We would like to have the ability to use this user look up in reporting with out have to create a seperate user look up.