First off would guerilla troops even be hauling around such heavy ordinance? My research points to no but I suppose since they are cyborgs they can lug these things around and their ammo.

During the Afghanistani war was the Mujahadeen had plenty of stingers on hand. Apparently they could transport stingers by whatever indigenous animals there were, in addition to traveling the countryside on foot with lots of extra RPG rounds. Stinger missiles can even be dropped via paratrooper.

So theoretically the indigenous life which I've heard referenced a few times in some magazine articles, akin to the sand worms of "Dune" I believe, could be harnessed in addition to any one driving in a vehicle. Or if the teleport technology present in Marathon is still in effect they could just be beamed in, used and disposed of? One of the things Bungie hasn't really commented on yet are the load carrying abilities of your troops infinite ala Quake or Marathon or is more realistic ala Spec Ops 2 or Rainbow 6? Although it seems rational that since the physics and everything else is so realistic that the load outs will be too but I guess that depends on your idea of fun.

As for current portable missile technologies the latest thing to hit the front line troops is the Javelin anti-armor rocket, which is replacing the Dragon as the heavy hitter for the grunts. Javelin is disposable, like the medium level AT-4. I do believe it's a fire-and -forget job. I don't see any reason against having a mag-fed rocket, aside from the immense weight. A great deal of larger U.S. rockets come as clustered units, like the Hawk (out of service?), Patriot, MLRS and especially smaller 2.75" rockets, Mavericks, Hellfires...It's all a matter of weight. Futuristic license would allow the size to be diminished, so why not?