Purchasing approval Hierarchies

 We have a business case as follows:

We are presently following the position based requisition approval hierarchies.  Requisitioning department is responsible to raise a requisition with mutliple approvers in the process. conventionally there could be more than one person under one position. We can handle the situation as per the assignment of active responsibility of requisitioner to only one person at the initiator level, what if the there would be more the one person against a position of approvers as system will be confused to whom the requested should be routed? What steps we can take to avoid such conditional approvals?