Fiberglass over foam may be a good way to do a new body from scratch. It would be light, sturdy, and quiet.
There is a how to article at
rqriley.
Maybe not quite as "eco-friendly" as you want to go, but a good possibility otherwise.
Is the contactor on the left of them all a reversing contactor? I see that it is left in even when the the drive contactors are replaced with a PWM controller like the Alltrax
Most electric motors can reverse direction by reversing the polarity of power to the motor. The only electric car I ever drove was an electric Geo Metro. There was a rocker button on the dash that said FWD-OFF-REV. You just press the button and hit the go pedal. That car was originally an automatic. Funny to see a covered up hole where the gear selector used to be.
I have an old golf cart motor I removed from a cart at a junkyard. Interesting to see how it was hooked up. It is almost the exact same one as is on the Citicar. On the golf cart, it was mounted at a 90 degree angle to the rear axle - just like how a drive shaft connects.
There was a reversing contactor and 3 resistance coils. The idea was like having a couple of "gears". These thick coils of wire resist that battery, so you get less voltage. Works just like a toaster. It also means you were using the same amount of power at any speed, but the slower you go, the more electricity got wasted being turned to heat. Only the highest setting connected the battery pack more or less directly to the motor.
(BTW - How do you go in reverse in the Forkenswift? Just shift to reverse I assume?)