Here is some use cases I came up with that Stephen G. wanted.

Case 1: Migration of servers.

Ex: Server A is a old model so were going to migrate the configuration to the new Server A. (You really have to be there physically there to mess with hardware / networking)

Case 2: Install / Remove Hardware.

Ex: Faulty RAM / CPU / Hard drive (That is not hotswapable) you want a quick way to identify the server and turn it off from a KVM inside the rack. (Not all company's will have a dedicated machine to SSH or go into a web-browser to configure these things. They may still have KVM's inside there cabinets.)

Case 3: Installation of server software (Open Source AND Proprietary).

Ex: Bitnami + your appliance, a appliance software stack where you can install it in a VM or locally inside a desktop. However you need to have a GUI to configure / start/stop / view logs to install locally. (They still have there own web interface in a browser but you still need a GUI to install it.)

Sidenote: Case 3 ~ When you install Bitnami + your appliance locally it uses the Container feature like Docker so it does not interfere with other configurations in the same server.

When I was doing my research at my University, I opted to give the user to use either the Ajenti, because it was a quick overview of your server / services that you were running. AND I wanted to have a configuration / overview control panel locally (That I was going to build in-house) so that you could have more advanced outlook on your server as well as local documentation, Hardware Install / Uninstall Wizard, and some other helpful stuff for the person. Because I figured that a small business didn't have a IT staff so it had to depend on ques from the software logs / messages and the documentation. But you could pretty much run the server from either both or one of them just fine...

I know for the beta and I think the full release you want just the base + essential server roles, and then later down the road your going to define more. How about you leave the essential roles for now that way you will have somewhat have a base to go off of other servers (ownCloud, Round Cube, HPC roles, etc.), BUT create a template so that members of the community can create there own roles and add it to a repo list. Kinda like having the Play Store on Android but for servers. I know you are still in Alpha phase but this is just something to consider, but I digress.

So those are my cases, hope this was some of help to the SIG.