Requisition approval process with same phase including parallel and serial routing

Summary

Requisition approval process issue

Content

Hello,

We have two different approval chain for a Purchase Requisition approval : project (group) and run (hierarchy manager)
To setup the WF we are using one phase Preapproval Header Hierarchy to define rules and conditions for the two chain run (serial) and project (paralell) because the system seem not to manage the mix define at the phase Preapprover header : first responder wins and header hierarchy

Our need  : using the same phase Preapproval Header Hierarchy  for the two approval chain

In one rule could we code a condition saying if we are more than two members in the approval group, when the first approver of the group will approve it will automatically push to the next approval step without the need than Laurent the other member of the approval group approve?