iExpense approvals - limit approver LOV to relevant approvers based on cost center signing limits

Requirement:  If the employee is creating an expense report for a cost center other than his/her regular cost center, the LOV for approvers should be limited to the approvers with signing limits for the selected cost center.

It's beyond me as to why the employee would not know who the approver is for the selected cost center when creating the expense report but the business requires this feature, nonetheless.  As per the standard AME flow, AME will error out when employee submits the expense for approval and his approval hierarchy does not have an approver with signing limits for the selected cost center.  Business would like the LOV for approvers to be limited to valid approvers based on the cost center when submitting the report.  The only way I can see this working is to use a