I was thinking the same thing a while back.. but since I've never coded, I wouldnt know how to start...
The best layout for me would include speedo, heading, music interface, and time. those are the basics that I would like. and I'd happily pay for that. Im not opposed to others additions, but would be careful not to overcrowd it.
how easy would it be to build a blank slate type thing, then all these options would be written as plugins that could be placed in whatever position each person wanted? Kind of like a second home screen with widgets? does that make sense?