My initial, and lasting negative reaction is something I trust. We could deconstruct it, if you like, and approach it a different way.

A soldier's IW is a confidence-building tool, and provides emotional security, as well as being a tool for fighting. Dismissing the soldiers' concerns based upon whatever trivia that can be gathered, scientific or not, is the "anti-leader" thing to do.

We have lots of relevant data: WWII USSR and Korean War-era Chinese/North Korean forces made substantial use of very ballistically similar 7.62 x 25mm submachinegun rounds. And units equipped with light weapons like this, did pretty well combined with heavier support weapons. However, there is also lots of data which suggest the round was not an effective incapacitator.

But here's some US Army reality for you:

The rollout of the PDW will be flawed. Training will be flawed. Funds for the sensors and "acoustic targets" will not be produced, (And soldiers will not believe "sensors" anyway) and NCOs who do not believe in the PDW concept will run the training. And the soldier will rightfully decide that the PDW is a piece of crap only good for letting the bad guys know where he is, so they can come kill him. (Which will happen, just often enough to shatter whatever confidence you think can be built up around more lightly armed troops)

I question the need to save weight by making the bullets smaller. History shows that "Army Leaders" will only make the soldier carry more crap, because they "don't have to carry heavy bullets anymore." Just look at how soldier loadouts went UP when changing from the M14 to the M16.

I think your concept makes some assumptions about reality, which cannot be easily proven by arranging neat and simple "facts."