Actually that IS what they're offering. What do you think Snow Leopard Server OS does? All of the things you just listed.
Hum, about those 2 points. That is precisely what OS X Server offers. iCal, Address Book, roaming profiles and centralized login. Those are services offered out of the box (amongst others).
Sure a lot of those features are built-in, but theyre not setup for a home environment. Its too geeky right now. You would have manually configure those services via remote desktop or by plugging your Mac mini Server into a monitor, which home users arent going to do.
iTunes serving is done by iTunes. Unlike some other platforms, there is no need to write a completely different app for something the existing app is designed to do. That's just a waste of development resources and complicates something that doesn't need complicating. Same for iPhoto.
It is very clunky to run full-blown iTunes to do I what I listed. You again have to remote desktop into your server to do basic tasks like change your Apple TV sync preferences, change ratings, etc. Home users arent going to do that.
Those features are already offered by other products. Backups of all your Macs is handled by Time Capsule. Why duplicate the functionality and waste the drive space on the Mac Mini Server for backups?
OS X Server actually already offers Time Machine server that does those tasks, but again its not setup to be run in a home environment and you need to manually configure it get it working on all your Macs.
Back to my Mac is obviously a Mobile Me feature. While it would be nice to have on a local scale, don't expect Apple to give it to you. Either set it up yourself using the included Web Serving capabilities and 3rd party Web apps or just subscribe.
Back to My Mac is also an AirPort Extreme and OS X feature. Im not looking to get out of paying for MobileMe, but lets be realistic youre not going to sync your entire iTunes or picture library to MobileMe. However, if a Web page was generated locally you could access it via Back to My Mac (or Bonjour Wide-area network which is the underlying technology behind it).
Apple actually offers remote GUI administration. Running iTunes from there is feasible on OS X server, so it can be done. So who cares if it's done from System Preferences or the iTunes GUI ? You have to VNC in anyway to set it up.
Home users care. Theres no way a regular user is going to remote desktop into a home server box to administer it. Microsoft knew that. Thats why they created Windows Home Server. Everything can be setup and configured without plugging a monitor into the server or using remote desktop.
Its simple to use. If Apple is going to compete in this space, thats what theyre going to have to do. And knowing Apple they could probably make it even simpler and better than Windows Home Server.
You act like Apple creating a server-side assistant, client console app and iTunes media server geared toward home use would destroy the mighty OS X Server.
It would probably boost its sales. What theyre offering now only appeals to small businesses and geeky enthusiasts.