For me, the rear wiper is a huge plus; but otherwise I'm totally with flunkysama. I'd like manual windows (I mean, the car is tiny-- it's not hard to reach across and roll down the passenger window...).
What I'd really like is manual steering. I got to try it out on a Ford Aspire for a bit, and it made me feel like I was picking up arm strength with no real downside. And the car would be lighter.
I dislike the thermostat climate control and I'd love to see it gone.
I would really like a decent sound system. And I'd like infinitely variable front and rear wipers, though I don't know if such a thing exists.
And I'd like decent cupholders--somewhere you could actually fit a cup, and easily reach!

My '83 Volvo had a tiny tray above the radio that was great for pens... That'd be nice. If they put the cupholders in, say, the doors, and the radio down lower, there would be a good space for stuff.
But yeah, I prefer simple changes, and less weight.