Add classifications to approval workflow conditions

It would be nice to be able to condition approval workflows by classification field values. We have two different sub departments in our construction department. Those two departments have different department heads that need to review Contracts/Invoices/COs, etc. Right now, there is no way for us to condition an approval workflow to go to the right department head(s). We do have classifications in the project that have values which could use as conditions in the approval workflow but the option is not there. This is prohibiting us from being able to use the approval workflows properly.