Currently the approval rule on invoice requests is set up with a stand-alone a list of approvers to select from, controlled through Configuration > Approval Rules. It would be incredibly useful if the approval workflow could be robust enough to handle setting approval rules by project attributes instead of by a list like this. A project could have an Approver attribute which lists those that have approval authority, and then approval for an invoice request would route automatically to those that have approval authority under the attribute. It would also be ideal to be able to set up some way to designate back up approvers or a hierarchical approval chain.