about the 40 mpg, I guess it could be achievable thanks to a twin turbo system, sequentials of course.
With the smaller one working at low revs, with a low inertia, a specifically tuned ECU and direct injection, it could work, even if that would reduce, even if slightly, the performance delivered at those lower revs.

apart from that, I can't bother of a car increasing the dimensions, so the weight more likely, and then loosing only 220 lbs of them.
I would prefer the present car (smaller and lighter) to receive those upgrades.
but if the only thing we can get, it's still welcomed.