if your really looking to stretch the boundaries, just a few exotic ideas of the top of my head
Making use of renewable and minimally invasive resources, using steam formed wooden vinear laminates for body panels. May not be cheap or cost effective at this point in time, but if enough capital is invested into the technology panels could be turned out relatively quickly.
Look at using renewable fibers for interior materials, such as hemps or corn husks etc, particularly trying to reduce the use of fossil fuel based materials.
Im not sure how detailed your design needs to be, but use of Crash structures, such as the ones employed in F1 might be beneficial.
again just a few suggestions from myself
All the best!
"I continuously go further and further learning about my own limitations, my body limitations, psychological limitations. It's a way of life for me." - Ayrton Senna