a lot was said there - great post!!
being a stirrer I'm going to go left field... and people can laugh it off or think about it
I've seen water burn (as director of a research company) so it sure can in certain circumstances, but that technology is not exactly available right now and has miltary as well as very big OEM and political interest. There are many patents also and not all of them require more power in to what comes out - think latent energy and reaction vs having to use a bunch of energy to get some back.
Water as fuel does create a new set of problems however that modern oils cannot yet address. So future water engines - if indeed we ever do see them in production (instead of just the various prototypes) - will require new lubrication chemistry so the water does not emulsify with the oil.
Water can be used 50% by volume as fuel - that was what Ricardo was doing during ww2. However as said - it must be atomised correctly which typically takes well over 100psi to achieve. Direct port water injection could use a direct port nitrous plumbing setup - but not the jets and solenoids - which should be dedicated for water as mentioned - such as Snows and ERL Aquamist etc... and should be ECU mapped not just dialed in. The old DIY converted windscreen washer units are a waste of time and may hydraulic your motor as solid water cannot compress so something else will.
now for something to think about: what would happen if you employed modern state of art direct cylinder injection technology to a direct water injector - and timed the water to spray directly after TDC as the fuel has been ignited?
clue: think the old stinky trains
You'd suddenly be able to either create a massive increase in power/tq or cut back on fuel 50% to maintain power. You would still have the water/oil issue so a water seperator in the oiling system would be required... but what you'd have is an Internal combustion and steam engine combination. 1 drop of H2O expands explosively if contained under pressure when it converts to steam - harnessing that at the precise point the piston is heading down is all you'd be doing. It'd require injecting water at common rail diesel pressures and at great timing precision.
back on topic - we ran 18psi boost at a true 9:1 cr with 24 degrees timing on 91 octane - with water injection (no ****). We could have run more had we turned up the water volume. We used an ERL Aquamist - it ran great.
another thing about detonation is combustion efficiency... most Vipers have poor quench so will be prone to detonate under boost (or require plenty of retard). The fix is a tight quench piston design, precision build etc.