I've implemented something like this myself for our Help Desk and like Andy suggested, using skills and star rating for each tier, works pretty well.
If your calls are being transferred from another queue, I'd make sure that you have a skill set for this. Some orgs are setup to strip skills on transfers, so on your In-Queue flow for the Queue, you might need to set the desired skill otherwise what you're hoping to achieve might not work as intended.
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Robert Niblock
Contact Centre Technology Analyst
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