Then a Subframe of Steel and top frame of Aluminum... Sheathed in a mix of Aluminum and/or Carbon and/or Plastics and/or Ceramics.
The concept of running on a frame instead of a uni-body chassis is not very different from this...
And if you consider that the push is to go green and eco-friendly...then it makes more sense to use parts fabricated from recycled aluminum...which would in fact be cheaper than Steel.
For that matter you can throw in components from recycled plastics. And even ceramic parts. Or tubular parts manufactured from Aluminum or Steel instead of solid members...like the Sway bars for example.
Innovation is just spanking Ford all over this. They just need to pick up the torch and incorporate much of what we've gained from the hypercar segment.