With all the flip-ups and aero tabs gone they probably have enough weight savings there (not that the cf weighs a lot to begin with).
Electric motors of high power are heavy, a mass loaded flywheel is also heavy. With Kers being optional, I bet some teams may decide to for go that option this season.
What they should have done is offered 100 liters of fuel for the race distance and completely opened the engine formula (if green was the real name of the game) The following season, 90 liters of fuel, etc. Unlimited tire changes of course. This would push road car engine development as well. This would put fuel consumption at .5 liter per mile which is far above where they are at currently.