This sounds a bit more like Smokey Yunick's "Hot Air Engine", which was turbocharged. Exhaust heat is the only reasonable method of accomplishing this, and with that much heat, much of the legendary detonation resistance of methanol and thus most of its benefits will be lost. The most influential factor on preignition/detonation is the temperature of the intake air, not the fuel or compression ratio.
The corrosiveness of the methanol will only be accelerated at higher temperatures.
To get that kind of reactivity, you've got to heat the methanol a lot hotter than the vaporization point. Methanol boils at 65 degrees C. I am certain that a heater/vaporizer using exhaust heat can be designed that will get the methanol (plus whatever water is "tagging along" with it) into the vapor phase, but well below any "pre-ignition/detonation" point.
"The corrosiveness of the methanol will only be accelerated at higher temperatures."
WRONG. You keep talking like methanol was some kind of horrifically corrosive chemical--it isn't. Water is FAR more corrosive than methanol (and in fact, it is probably the condensing water that is doing most, if not all, of the damage, anyway). As long as the methanol and water are in the vapor phase, NO corrosion will occur. You've got to have a LIQUID phase to get corrosion, because the corrosion is fundamentally an electrochemical process--and that requires a liquid capable of ionic conductivity.