Split "assignee" into multiple fields

[Paul Miller]

I would like to split asignee into multiple fields to track different parts of the workflow. 

For example, for a bug, I might have "assigned to fix" and "assigned to review" instead of 1 "assignee" field.  

Ideally, I'd be able to split into an aribitrary number of fields. 

[Joe Pitt]

You would need to create a custom field for that. the Assignee field is a system field and is used for several built in reports.