Problem with Forecast because of the hierarchy of the users

Hi, heres what I want to do with an example:

In configuring forecast, I have 2 roles that are in the forecast, Sales and Administrator.

I know that the users in those roles need to have a Supervisor or another user to send the forecast (Like hierarchy, i dont know if you understand what I mean).

But I have a problem, because there is a user who is the Administrator, but also a sales person, so he wants to forecast his opportunities also, but he is at the top of the hierarchy so you cannot assign him someone upper than him.