A couple of things:

1) I WOULD TOTALLY BUY THAT!

2) If you make it out of regular plastic, those who want the carbon-fibre look can send it to that place to get it coated. I also know a place that metalize it with vapor deposition.

3) It would be good if the cup holders were adjustable in width, maybe there are OEM cup-holders from some other mainstream car that you incorporate into the design with this feature.

4) A change box would be nice, I use the square closest to the handbrake for change.

5) I really like the idea of a hidden compartment or two, maybe underneath one of the cupholders.

6) How about a lighting option to better illuminate the footwells. I'm thinking clear circles, maybe an inch in diameter one on each side pointing out horizontally into the footwells. Then inside wiring and a single 1 watt (or maybe 3 watt) lumileds/luxeon LED.