Purchase Order Approval with AME (R12)

 I know that purchase order approval using AME is not supported by standard functionality.  Position  or Employee / Supervisor hierarchy are standard for PO.

However I would like to hear from anyone who has implemented of contemplated implementing such a solution.

Due to complex PO approval requirements we are evaluating a custom solution.  For example: customise the PO approval workflow to reference dynamic AME approver groups.

Thanks

Glenn