Secondary Arnament are the box missile launchers: just assume Striker Missiles: six Anti-Vehicle, six anti-perssonel. Fired by Driver.
No no no no. No. All except this. The driver drives, and only drives... unless they're a rigger, and even then, if the corp/govt sponsor can casually slap a VCR into the heads of their tankers, they're still better off with dedicated drivers and dedicated gunners. At most, there might be a hull LMG/MMG the driver can operate, but that's usually a last resort weapon for infantry rushes, which really shouldn't be happening in the first place, against armor.
However, since the driver has limited visibility, even with drek-hot sensors, and the gunner has target-focus blinders on, a missile rack (like the external MG) would be better operated by the commander, whose primary job is to use their position of superior visibility to designate targets for the gunner and call for (and assist in) fire from specific weapons as well as to direct the driver's course. There's no reason the gunner couldn't be asked to fire them instead of the main/coaxial guns, but the commander should be using them on defiladed targets or on targets outside the gunner's quick-traverse field (and if there are too many of those, then s/he has slotted the barghest already, and has probably advanced to a phase line beyond where they can be supported. Or the plan/order-of-battle was total drek to start with).