A method I have often thought over is to engage 1st person view when peeking around obstacles, select weapons like sniper and by player choice, f1 or similar.
This would be further supported by cutscenes and be an integral mechanism for playing the game.
Too much and you will end up with a curiosisty maybe, neither one or the other.

I think Camz over shoulders should sway over to the side chosen for 'look' so if your on left of screen and you want to look left, swing around and let the camera shift over to the right too but maintain over the head and back for most of the time, a 3 stage camera orientation mechanism for what you have discribed.