Enable Approver to change status to "Waiting for customer"

[TB Group]

I have set up a "Service request with Approval" so that an approver can check that all information requested are provided by the customer before the request can be sent to the assignee.

Currently, the approver can only "approve" or "decline" the request, and if the approver decline, the request will be considered as resolved. 

Instead of "declining" a ticket, I would like him to be able to ask for additional information in comments and set the ticket to "Waiting for customer" so that the customer can edit his request, and so that the ticket is no longer queuing in the Approver's queue.

When the customer has added the information, I would like him to be able to reset the status of the ticket back to "Waiting for approval".

Can you provide some guidance on how to achieve this?