Approvals - supervisor hierarchy / most senior position

Summary:

We have many tasks (absence, salary, promote, working hours etc.) that follow the supervisor hierarchy for approvals. How can we set a different approval rule for the person in the most senior position who does not have a supervisor (as we cannot have a manager loop issue). Likewise any other positions that reports to someone in another part of the business that does not use the Oracle application.

Content (required):

The most senior position does not have a parent position and the incumbent does not have a line manager as this would create a looping issue. What options are available for us to set a different approval rule/route their own MSS transactions to someone else? Also required for positions/employees who do not have a line manager and so their approvals fail.