But update it to what? If it's just a typo situation and the administrator can easily determine which operator id was meant then sure this can be addressed. But what if, as you say, the operator was deleted from the database? Or what if due to the typo the intended operator id cannot be discerned?
I recommend, therefore, that before the assignment that uses this assignee param is reached, you have a utility shape that verifies the parameter is correct, and if not, routes to a retry assignment of some kind - either to the create operator, or an admin, as appropriate. That way by the time you reach the assignment shape, you are sure the assignee param is correct.