This discussion appears to me to be like trying to decide what size and shape of logs to throw onto the fire, to warm a pan of water, when everyone else is blowing sawdust into a boiler with air....
I am sure someone could make a water injected engine work, although I cannot see the advantage or useful reason "why", but of the thousands of different ideas that have gone before, the historical record shows what people could make work, and their failures were "lost" as useless.
I do accept, there may be some hidden gems of history that didn't work because of the available materials, or other reason, but if there was a way of making this water injection engine work thermodynamically, and efficiently, then I fervently believe it would be in the record somewhere.
Considering that the earliest Jet engines, (Non-Whittle that is) were really use of the directed exhausts from hugely powerful supercharged or turbocharged aero-engines and similar (Like the Napier Deltic, Sabre, etc.) through jet nozzles at the rear of aircraft, then someone decided that reciprocating engines were not the best combustion chambers for a jet, so then Rolls Royce believed Whittle's ideas and are fundamentally what we have today, I think that is an example of how the apparently crazy ideas have all been explored and developed to the point where the "survival of the fittest" rule has left us the technological world of today.
Remembering the that steam is (like electricity) a means of transmitting power, not a fundamental source of power leads us to burning fuel inside the cylinder, rather than generating steam inside the cylinder. We all know: Fuel burning in a firebox (combustion chamber) to generate steam, then to utilise the power from the steam, has become fuel burning inside the engine as a combustion chamber (at higher pressure than the conventional steam plant), to generate power directly. I.E. cutting out the steam power transmission from combustion chamber to cylinder. Thermodynamically, there is no advantage to generating steam inside the cylinder, simply to eliminate the boiler and plumbing.
Sorry to put a damper on this discussion.