I see, you posted in the rules clarification and I'm sure you get the same answer there.
Also check out
this thread. Especially answer by Heretic87 at the end. Basically you want department members to have positional authority and be subordinate to department head only. Which I think is an overkill. You know what the elevator operator disorder is? When some person gets some little piece of power and then becomes a massive dick about using it. In CM this generally happens with CT or MPs, I don't think we should encourage this.
Also, SO is not a department head.