Using Supervisor hierarchy in Purchase Requisition Approval with AME

We are in 12.1.3. Currently Purchase order approval is designed with Position Hierarchy. Purchase Requsition is designed with  AME Approval. Now Purchase requisition  Approval has to be redesigned   with additional rules for AME. There is a need to use Employee Supervisor for specific set of  Approvals. For example,

1. To find the Requester's  Name ( not the Initiator's name).

2. Get the Requester's Supervisor ( from Employee Definition-> Supervisor) and Route for Approval.

3. If the approval Limit not sufficient  in setp2 , then it has to be routed to  Supervisor ( Supervisor  of Approver from Step2).

In the same way it has to be routed to Approver's Supervisor untill the Requistion is approved.