add AppArmor kernel support (Ubuntu)
SELinux is the only offered alternative. SELinux is not easy to maintain and audit by comparison.
Yes apparmor is very important for security and should be included. It is part of the default Ubuntu installation, so I see no reason why Rackspace cannot include it.
Yes, apparmor is a great security feature, and is installed by default by the normal Ubuntu server. So Rackspace should definitely consider add this.