Not sure. As far as morale hits it's been done before but I don't know if anyone really understood how it functions except for the developers who came and went from the project in Resistance and Liberation. And it was hardly a serious effort by serious developers there.
Basically we're talking about tracking proximity of bullets and people and preferably a lot more work in animations to go along with it.
With the audio of bullets zipping by I understand that the player's proximity to a bullet miss is already tracked in some measure otherwise you wouldn't hear that. You also have local voice chat so presumably the game can track your relation to other players.
With animations... just in general, I strongly feel like you should be able to resume reloading from certain steps, reload while moving to some degree. Fumbling would help with any game in any time period and we know it's realistic especially under pressure.
The most basic effect on the player would be weapon sway from shaking and we already know there's that annoying effect when you first take aim. There seems to be already be the ability to blur your vision. Tunnel vision... some heartbeat sounds, heavier breathing
A carefully thought-out process and testing would help.