has anyone used or created a cost center in netsuite?

Unlike SAP NS have more cost segmentations than just cost center - Class, Cost category, dept, location, custom segment etc. So there is no exact cost center in NS, instead use the above segmentation

In the past. We renamed Department to CC, then had to assign CC approvers for PO approval WF.

custom segments are one of the best feature of Netsuite unlike other traditional ERP's