Approvals At Top of Org Chart

Summary

Wondering if anyone has existing info on how to manage approvals at the top of the organization hierarchy.

Content

An important aspect was missed in the approvals of expenses on our implementation. Essentially what we need in a corporate sense is for the "president" of the company to have their expense approvals go to the CEO and the CEO's to the CIO. In our org chart all of these positions are peers in the hierarchy (including the president).

So, in short, how would we manage approvals between organization peers at same level (i.e. they don't have "managers" to approve)?