The allies were using what they had handy to eliminate knock, but carrying all that water lowered the aircraft payload, and it only offered 10 minutes of 'wartime emergency power'.
The Germans were making synthetic fuels which resisted knock, similar to you just running e85, which is the better option.
Unless you could automate a low water/meth level boost drop into the map, and guarantee the system won't surge around corners when low, I doubt any tuner will rely on it for knock protection. (unless you signed a disclaimer or similar.)