Here's my top ten list:

1) Improved steering and directional stability at speed.

2) Better seats with optional heating and adjustable lumbar support.

3) Oil change interval monitoring by computer - by todays standards having fixed 5k mi intervals is archaic, and wastes oil - very un-green. Have computer monitoring of intervals combined with synthetic oil, and changes can easily be stretched to 10 - 15k miles.

4) A real premium stereo that deserves the name - dump JBL! Get Bose or Harman Kardon.

5) ABS needs better tuning: if you run over a bump while braking, braking essentially stops for 1-2 full seconds, way longer than necessary and quite dangerous.

6) I like Bob's idea of removable extra battery pack, as a plug-in.

7) Another of Bob's ideas: exhaust heat recovery, not just for heating, but maybe also via peltier elements or a more efficient system, to help charge battery.

8) Photovoltaic windows, maybe paint, or roof panel for slow charging while parked in sun.

9) Bob's again: no side mirrors, instead cameras on sides and in back, that provide one single wide angle view, either via internal rear view mirror, or via center dash display.

10) Any trick to improve highway cruising fuel economy: PSD lockup, maybe also lowering of car by 1-2 inches at speeds above 55-60 miles per hour, underbody streamlining, maybe integrate radio antenna into rear window, and maybe also have a receding rear window wiper that disappears into the rear spoiler when not used.