Nice job !
However , ispconfig php should be instructed to symlink phpmyadmin and /webmail in every newly added site .
Aint nice to force clients to remeber server IP or server hostname to acces the above as http://xx.xx.xx.xx/webmail
or phpmyadmin instead of their domains.
And yes , How do i enable clients to modify theis databases permissions ( Select , Alter , Insert )
As far as i can see , only sql root user can do that.