I recall in the early 2000s that they had a local manufacturer donate a hydroformed aluminum frame. I don't even want to think about how much that sucker cost. Since they had the truck apart, they started chucking/replacing other parts.
That savings in weight allows you to accommodate more batteries, improve towing performance, or just improve fuel economy.
If I remember correctly, my school's team ran a series hybrid similar to the parent. They might have had regenerative braking, not sure.
If you are planning to sell this as a kit, replacing the frame isn't really an option. I'd focus on the motor (duh), battery size and location, regenerative braking, and lightening components that can be easily accessed.
What you might want to look at is working from a crossover SUV platform. Unfortunately, those car/trucks tend to be pretty damn heavy too...