Our membership program should not be thought of as traditional shared hosting. We do not allow unrestricted plugin installations due to security concerns. Since plugins are created by third party developers, many have security vulnerabilities that users aren't aware of - that can cause major issues for you.
However, we will be periodically reviewing plugin suggestions from our clients and updating our system with plugins that we feel are safe to use. So if you would like to suggest any, we would love to hear about it.
Thanks for helping us keep the the membership program useful and safe.