how to prevent invoice requester to be the final approver in approval spreadsheet?

Summary:

hi all, we have many approval rules in the approval spreadsheet, and sometimes the skip rule of a condition may be accidentally missed out/set or some rule confusion that lead to the invoice requester approved and the process stopped making the requester as the final approver.

We want a way to prevent this to be happened as a final gate, we tried the prohibit self approval in the BPM setup of the invoice approval but this will block the requester to approve at all, we want the requester as the first level of approval but not the final one.