mgb
The server-manager already does the role you describe.
When you enable or disable functionality, appropriate services are started/stopped and appropriate ports are opened/closed.
In a default install many services are disabled anyway, until you enable them in server manager, so only a minimal set of services are running and ports are open, say in a default install of server gateway mode.
You also have further control (beyond what server manager offers) with simple db commands to limit public/private access or enable/disable services. Most of the commands are listed in the FAQ and Howto pages, so look and read.
You can easily come "unstuck" with a services control panel like sme7admin or similar, as you may disable a service that you actually need eg mail - you will no longer receive admin emails, web server - you will no longer be able to access server manager.
Be very careful using such a control panel, as you may turn off something that sme actually needs.
Services and ports control is integrated into server manager (& the underlying code/db commands) for all common requirements, so use server manager the way it was intended to be used.