Voltage Regulator

I would takea multi regulator approach to solving the question.

Texas Instruments makes a few Switching Regulators that will take the 12 volt input and switch it down to something like 5 or 3.3 volts.

What you are concerned with is the input voltage width allowable (say 15 to 18 volts, on down to something like 8 - 5 volts.

Look here http://focus.ti.com/docs/prod/folders/print/ptn78060w.html

for one such example.

(Found by Google of "TI switching regulator 12 v in"

From there, I would look at some of the smaller regulators (posibally linears) to get to the 1.2 volt Vccint, etc.