The concept seems simple, but I have no idea how difficult the implementation would be.
Use the HDMI as video out (it looks fine when I plug my Coby Kyros into my TV, seems a phone would be the same / better). Use the USB as a mouse - I know that Android is designed for touch screen, but I thought you could use a mouse for it.
Anyway, the concept seems simple, but perhaps my concept oversimplifies the matter.
If a 3rd party vendor could make a device independent dock, and price it reasonably, I think it would sell like hotcakes. At least, the same people that would buy the Coby (like me) to root it and do what they want with it would buy a 3rd party dock and use it with their phones.
My wife, who doesn't overly love technology, loved her driod when I finally conviced her to get it. If she could get a dock for it, she would likely never use her laptop.
A device specific dock seems ... ridiculous, for an open source platform.