My suggestion, make the limits have an option to behave like they did in Plesk 8.x, 7.x and probably earlier. In those versions, traffic and disk usage were allowed to exceed the limit if you chose to allow it but email accounts, databases, etc. were not allowed to go over the set limits. In 9.x, if you allow over usage at all, it allows over usage of everything and then sends customers confusing notification emails about being over their plan even though the email doesn't include what they're actually over on since they only include disk and traffic. We bill for going over on traffic and disk and do not want to allow customers to go over on email accounts, etc.; we can no longer prevent that since we can't shut sites off when they hit their traffic limit obviously.