Exemption from jury service is the privilege of the person exempt, not a ground for challenge.
However, when multiple parties having adverse interests are aligned on the same side, three peremptory challenges are allowed to each party represented by a different attorney, and the court may allow the opposite side a total number of peremptory challenges not exceeding the total number of peremptory challenges allowed to the multiple parties.
"Each of you do solemnly swear (or affirm) that, in this action now before the court, you will justly decide the questions submitted to you, that, unless you are discharged by the court from further deliberation, you will render a true verdict, and that you will render your verdict only on the evidence introduced and in accordance with the instructions of the court, so help you God."
Mich. Ct. R. 2.511