Add Approval Workflow to an Estimate Merged

A prospect has many estimators preparing estimates and they have an internal workflow that requires an estimate be approved prior to issuing to a customer. While there is an approver identified on the estimate, and we can create a status entry of "Submitted for Approval", there are no controls on whom can change those values. I suggest that a similar approval workflow, like those that exist for financial transactions, be added to an estimate. I suppose the response workflow engine used for submittals could also be leveraged