Now that I consider it further, a whole separate seat and set of controls for these gun emplacements seems overkill. You could just use them by pressing ^ and then moving in their direction, like folding bikes. Or even just the tried and true ‘e’ command we’ve all grown to love.
Once you do this if force equips you with a placeholder weapon ((Example: GAU-17/A gatling)) it blocks you from moving or doing anything beyond firing the weapon/releasing the controls.
This way it would still be subject to the same equalizers as normal firearms, such as player skill, bad traits like trigger happy and current encumbrance. You could even set up an emplacement directly in front of your driver seat, at the expense of leaving yourself open to enemy attack and having to choose to either operate the gun or steer the vehicle.
Also, give them a firing angle and facing position just like when installing headlights. ((Could probably add that to current vehicle mounted turrets as well to cut down on the friendly-fire related deaths.)) When operating a gun emplacement you can only fire at things in the emplacement’s cone of sight ((You could represent this visually in a manner similar to the artificial night generation bionic)) This leaves the gunner, PC or otherwise, still very vulnerable to flanking.
