You were talking about changing the intake for the coolant to vary with need of cooling, have you thought of a heat exchanger for the intake air for combustion or for that matter from you exhaust, routing the cool air through the rad, then to an exhaust heat exchanger then to the engine, in effect reclaiming the heat that would have been waisted... there is an interesting article in Popular Science about using the heat to produce steam in the engine...
http://www.popsci.com/popsci/technol...cbccdrcrd.html