Nested Sub Accounts

Hello,

I want to create the following users like
End User

Manager

Purchaser

Each end user will be mapped to a manager and each manager will be mapped to a purchase

When the End User places an order, it goes to the Manager for approval and then after approval from Manager, it goes to Purchaser. Now, I know that one level of my requirement is possible through Sub Accounts. But can I create nested sub-accounts? like sub-account within a sub-account?

Is this possible?