Hey Rodrigo,
There is a different way of solving the same problem. Verify SaaS supports advanced workflows, whereby you can configure a group of reviewers upfront (Upto 25). All of them can technically be on-point to do the access reviews. So, even if somebody is on leave, you can expect the others to review the same. This is definitely not delegation, but the capability alleviates the need for an explicit delegation, bringing in a better experience.
It is not necessary that you configure 25 people in a group, but you can always have a reviewer and a couple back-up reviewers packaged in a group of reviewers and use them in your flows, as a defacto.
Another capability that we have with Verify SaaS is the Timeout based Escalation. So, you can configure that a specific request is to be actioned in 7 days (Anywhere between 1- 15 days), failing which the request escalates to an Escalation Participant / Approver. This arrangement also aligns with the notion of a back-up approver, in case the approvers are not doing their duties in the specified time, irrespective of the reason (leave, efficiency, work pressures).
Let me know if that helps.