Setting appraisal_user_assignment.jobassignmentid to null may allow users to re-select their job assignment (it may be assigned automatically, either on cron or when they next access the appraisal, if they only have one job assignment), and the new manager or appraiser may be written into the correct place in the appraisal_role_assignment records. Or you could manually update the appraisal_role_assignment records. But I have no idea if there are other consequences, or even if it will work as intended (Does it work with dynamic appraisals on or off? Multiple jobs on or off?). If you want to try this then I suggest cloning the site and testing it on the clone.