A setting where you could inherently customize where your hands lay on the grips of a gun. For instance if you take a look at onward, plenty play and guns are very different when it comes to size, shape, and once you aim they all have different points on an axis where it meets your eye. I would suggest allowing each player to set their own axis for the hands allowing the gun to move left and right up and down, and also move closer or farther upon pickup.
Example: Onward Calibration System.