When someone needs to cover a big swath of terrain in real life, they call in the support gunner or mortar man. While there are stationary turrets and precision strikes, they are either impractical for use in close quarters or rough environments, or are simply too big and expensive. This is why there needs to be an item to fill the role of small-scale direct or indirect fire support. These, of course, would be man-portable turrets and mortars.
On the subject of man-portable turrets, they would be small-caliber, LMG-styled weapons mounted on a foldable tripod and deployed on the ground to shoot things. An example of this would be an M240 on a tripod. Having it being man-portable allows direct fire support to reach positions where LAVs can't, such as inside or on a mountain ledge. In addition, the target would be much smaller. But the ferocity of a mounted gun would remain, making it a viable threat.
http://upload.wikimedia.org/wikipedia/commons/thumb/3/39/M240E6_M192_Tripod.jpg/640px-M240E6_M192_Tripod.jpgThey'd be lightweight enough to carry around on your person in the equipment place, but still be a large drain on power and CPU. In addition, if you do have them on your back, mobility will suffer. You're not running faster if ~20 pounds of fun are occupying space on your Batman utility belt. They would also take quite a bit of time to set up, and once they're in place they need another long while to pack up. If a portable turret is put down, the merc handling it would be stationary, and have a limited range of motion (you cannot swivel it around 360 degrees, for instance.) The concept of deployed turrets works similarly to Battlefield 3's bipods, but with longer deployment times.
Ammunition for these turrets would be limited, on par with or maybe a bit over an HMG. This is mainly to balance out the good amount of damage it deals.
Overall, a man portable turret is great if you have a team supporting you with security, targeting data, and ammo. But alone, you're likely to get flanked (and even with a team a well placed grenade will end you.)
On the other end of the spectrum are mortars.
http://upload.wikimedia.org/wikipedia/commons/thumb/f/fb/Mortar_firing_Iraq.jpg/640px-Mortar_firing_Iraq.jpgMortars allow someone to reach out and touch their enemies with indirect fire. A nice explosive shell will be deposited right by the enemy's head, probably killing them. But, as it's indirect, targeting will not be accurate without someone spotting for you. Ideas for targeting include a little map like Battlefield 3's mortar system, or a "blind" system where you see a dotted line indicating trajectory in your first-person view and you walk your fire over to the enemy based on observer reports. And like the turret, the mortar would be stationary, vulnerable, and have limited range. The trajectory can only go so far out or in, maybe with a minimum range lest you point the mortar 90 degrees up and kill yourself when the shell boinks you on the forehead. And before I forget to mention it, the caveat for shooting off your mortar is a big 'ole target marker that screams: "I am a mortar man. Shoot me now."
Both of these pieces of equipment require teammates to work, and it is absolutely not a one man operation. If you don't have a coordinated squad going, you will get flanked and die, or you won't hit anything. They'll add a good deal more teamwork to the game, not to mention them being really cool.
Pointed out problems:
Any suggestions for this? Comments? Problems?