AP Payment Approval rules

Summary

need a back-up approver in case Approver is not available

Content

Hello all,

In BPM PaymentApproval task, the Approval rules have been defined with Approver as Approval Group (a specific user account has been added). I know there is no Parallel Approval - First Responder Wins. I'm wondering what would be best way to create a rule, it needs the approval request goes to several approvers and first responder wins. 

If you add several users to the Approval Group then approval flow goes to a path where everyone has to approve the transaction in the order they are added in the group. So that does not work for us.