Really? Where is PSP in your picture?
It would be a Media Renderer and a Control Point. It would enable you to playback network content using its own playback capablities or control the playback of another device. It's capabilities actually make it very suitable for this.
There is no reason why a PS3 can't be a Media Renderer, Media Server *and* Media Controller.
True, but it's a bit overkill for a Media Renderer. A more dedicated device would be preferable. Especially if you want to minimize duplicated functionality. I'm not saying the PS3 is bad in any of these roles. I'm just saying dedicated devices would be better, providing it is your intention to do a full build-out.
So my vision would be a system where the XMB-based UIs tie all the devices together. Learn one, and you can quickly learn the rest.
An example system could have:
Multiple DVRs
Multiple Media Renderer devices (which may or may not include BR drives)
A BR disc jukebox (100+ disc) that automatically downloads movie info upon disc insertion so these discs can be easily browsed from the XMB interface.
An Hard Disk-Based Media Server
A PC (pretty much still the best way to acquire, edit, and reformat content that's suitable for playback on all these different devices). This can also serve as the Hard Disk-Based Media Server.
A PSP for mobile viewing and control.
From a hardware standpoint I think this would be an ideal system (I didn't include the TVs, receivers, etc). And using a single UI model would greatly simplify system operation.