Alright, so let's start from the beginning:
1) it is possible to generate a backup with just a user's login. You call the API1 function Fileman::fullbackup via the XML-API
ApiFileman < ApiDocs/Api1 < TWiki
Once this has been done, call Backups::listfullbackups to monitor for the creation of the new file
ApiBackups < ApiDocs/Api2 < TWiki
This can be downloaded via the instructions in the API docs (you should be able to do this with reseller login, however your milage may vary).
2.) inside of 11.25.1 we have added a new call called "backuprestore" that will allow you to restore backups, this can be used to automate the restoration process. That being said, /scripts/restorepkg is probably preferable.
3.) You can generate backups via the CLI using SSH via /scripts/pkgacct $accountname. This will only work as root