I have no idea if this is possible with the existing FMOD library, but after playing Half-Life 2, I've been exposed to stereo sounds for weapons. It's so much more convincing than a mono sound.
Doom uses positional sounds for everything. By design these have to be mono. I have no idea how Half-Life 2 is doing this without either cheating (play something different for the player shooting the weapon) or just mixing multiple sounds from different positions together.
Here's a thought...For stereo sounds to be played in the distance, use mono sound curves, in other words as the player gets farther away from a stereo sound, it merely decreases in volume (no speaker positioning is done).
Eww. What I'd do is just play two seperate mono samples 1 or 2 units apart (the "left" sample would be played one unit to the left of the source, the "right" sample would be one unit to the right).
That depends on the sounds being played. But keep in mind that using stereo sounds in such a manner is cheating. The stereo effect in real life doesn't come from different sounds but mostly from any kind of reflections and those are not that easy to emulate on a computer. A gunshot has a single point of origin and hence absolutely no stereo properties. So the big question is: How do you emulate it?
How well would that work in terms of player-origin sounds (ie. pistol shots)?
It should work fine. The left sample would be played to your immediately left (which would cause it to pan hard left), and the right sample would play immediately to your right (which would cause it to pan hard right). The only thing that would mess it up is if you had variable pitched sounds on, since it would, in essence, split the single stereo sound effect into two mono sound effects.
I wouldn't mind if Randy "cheated" with the stereo sounds - my main reason for requesting this is because I'd love to use some HL2 weapon sounds, but they are absolutely destroyed if I change from stereo to mono.