Well I gave it a test tonight, albeit only the backup functionality, and all seems to be working. I missed the bit about deleting the original BackupMenu.item within /etc/bootmenu.d as the new version is backupmenu.item (all lower case), and so the one in extras-devel was being launched instead at first. Once I figured that out though then all went swimmingly. The new method is much faster than the old one although my rootfs tar is slightly bigger than the img. Maybe the tar's could be gzipped as well?

I'll test out restoring a bit later, if I am brave enough.. ;-)