PHP, What do you need for a full Server manager?

Question

I will soon be making a Debian-based OS and I was wondering what are the main things that a Server Manager would need to include?

I already have a few ideas:

Package Manager.
Ability to restart.
Manage: sites, users, pages, blog-posts, comments, etc.
Email Manager.
VM Manager -- If VMs is enabled in the Package Manager.
Storage Manager.