Can I use a CIviCRM Webform URL in place of the required action.unsubscribeUrl?
You can already disable the setting so the tokens aren't mandatory, then use add your url to the webform (with the contact id and token checksum so they are "logged")

It's under Administer>civimail>civimail component setting http://d46.demo.civicrm.org/civicrm/admin/setting/preferences/mailing?reset=1