Ethanol, from cellulose or corn or sugar cane, does not have lower GHG emissions than gasoline.  The illusion of cleanliness is created by a misperception of the nature of soil and the carbon/CO2 cycle.

You are claiming that since the plant mass used to make the fuel, removed CO2 from the atmosphere, you can simply subtract that amount of CO2 from the amount given off when the ethanol is burned to find the total GHG effect of fuel farming.  Adding a bit of CO2 for oil based tractor fuel and chemical fertilizer.

Here is the flaw, the plant mass already growing on the land used for ethanol production, actually did remove CO2 from the atmosphere and sequester it in the soil, before it was used for chemical agriculture and eventually fuel farming.

Furthermore, millenia of carbon was stored in that soil before it was exploited with chemical agriculture.

Electric power from renewable sources actually does prevent GHG production.  Ethanol production prevents CO2 from being sequestered year after year.  To the tune of 1.8 tons of CO2 per acre per year in the case of prairie land.  That is the same as releasing more cO2, from the point of view of the carbon balance.

The Audi plugin has the potential to be much cheaper to manufacture than hybrids like the Prius, with complicated series/parallel transmissions.

It's true that a series hybrid with a much more efficient generator could have much higher average mileage than the Audi.  Something like the Boeing solid oxide fuel cell/turbine that they are developing for backup power on their airliners.  It is 60 or 70% efficient.

As far as adoption speed, regular cars do not do well on ethanol.  Flex fuel cars would be a big capital mistake if better, cheaper batteries like the Firefly design go into mass production soon.

Firefly has its graphite foam lead acid battery coming out to the semi market right about now.  This design doesn't suffer from material shortages.  

You cited silicon as an example of shortage that increased the price of the end product.  Only refined silicon is in short supply, with silicon being one of the most abundant elements on earth.  Depite refined silicon shortage, the cost of silicon based computing devices per computing power has dropped precipitously over the decades of the computer age.

Plugin hybrids don't need expensive quick charge batteries, hours long recharge is fine.  Pure electric plugins will need quick charge nano tech batteries.

I don't know much about the efforts to increase ICE efficiency, but I see it involves adding computers upon computers and excessive complication to achieve small incremental advances.  Plugin hybrids are a huge advance all at once, in the case of the Audi design, with a lot less complication.

A 50% increase in efficiency in an ICE could take a 40 mpg car to 60 mpg.  A plugin hybrid could average well over 100 mpg.  Probably over 200 mpg.

As far as speed of rollout of plugin hybrids and a renewable smart grid, that will take time.  But these technologies both coexist well with the present system and chip away at it.  

Solar panels can be added onto the present grid, and smart grid devices added to store that power as cooling or heating or as battery power in plugin hybrids.

All the technologies you are invested in have a rollout time as well.  Cellulosic ethanol is lagging behind its promised rollout year after year.  I think plugins powered by renewable electricity will beat the rest, mainly because a gallon equivalent of electric "gas" costs 66 cents.  With solar panels on your roof, that payback in a few years, that cost quickly drops to near zero cents per gallon equivalent.

As a gallon of liquid fuel, gasoline or ethanol, rises inexorably through 4, 5, 6, 7...  dollars per gallon.  You can't claim ethanol will reduce liquid fuel prices, since we only have enough spare biomass for maybe 10% of liquid fuel to come from ethanol.

Put your money on the smart grid, internet enabled power grid that carries all the information now traveling through phone lines, cable tv lines, and cell phone towers, and uses distributed computing to smooth out the supply and demand on a 100% renewable power grid.