In my scenario we want to customize the access request page. We already know how to create an application page, and with a powershell command, instruct sharepoint to use that page instead. http://blogs.msdn.com/b/ramg/archive/2009/11/06/supported-way-of-replacing-application-pages-in-layouts-directory.aspx
When the user gets to that page he will be able to send a custom message to the person responsible, the custom app page we are creating will also put access requests on a custom list.
When the admin checks the custom list, there will be an Approve and Reject buttons for each item in the list.
The questions is how to approve programatically an access request?